Astronomer wrote:
Which commandments?
For example:
Genesis 9
6 Whoso sheddeth man's blood, by man shall his blood be shed: for in the image of God made he man. 
Astronomer wrote:
 If I failed to uphold the law, then I was to be killed.
 Not necessarily. Some crimes were punished with beating, fines, restitution, maiming, so on. Death was never the only punishment.
Astronomer wrote:
Yet, there was a way for me to regain that holiness by sacrificing a spotless lamb, goat, ram, whatever the circumstance warranted.
 The sacrifices were symbolic of Christ.
Hebrews 10
4 For [it is] not possible that the blood of bulls and of goats should take away sins. 
Astronomer wrote:
This means we do not have to follow the law to be pure, but rather we should follow Jesus' laws, for those 'trumped' the former laws.
 The only thing that Jesus changed was this:
John 4
21 Jesus saith unto her, Woman, believe me, the hour cometh, when ye shall neither in this mountain, nor yet at Jerusalem, worship the Father.
Luke 21
6 [As for] these things which ye behold, the days will come, in the which there shall not be left one stone upon another, that shall not be thrown down.
Israel ceased to be a nation of Priests. The law which always bound all men is still binding.
1 Timothy
9 Knowing this, that the law is not made for a righteous man, but for the lawless and disobedient, for the ungodly and for sinners, for unholy and profane, for murderers of fathers and murderers of mothers, for manslayers, 
The law was never contradicted in the New Testament, rather, the doctrine of the New Testament was argued by quotes from the Old Testament law.
1 Timothy 5
18 For the scripture saith, Thou shalt not muzzle the ox that treadeth out the corn. And, The labourer [is] worthy of his reward.
If we do not follow the law, then we are liars, murderers, adulterers, witches, so on.
1 Corinthians 6
9 Know ye not that the unrighteous shall not inherit the kingdom of God? Be not deceived: neither fornicators, nor idolaters, nor adulterers, nor effeminate, nor abusers of themselves with mankind, 
10 Nor thieves, nor covetous, nor drunkards, nor revilers, nor extortioners, shall inherit the kingdom of God.
We can not be pure if we do not follow the law. Only God can purify us from the guilt of not following the law.
James 2
20 But wilt thou know, O vain man, that faith without works is dead?
21 Was not Abraham our father justified by works, when he had offered Isaac his son upon the altar?
Abraham was justified by faith because he followed the law that God gave him.
Astronomer wrote:
We should be like Jesus, sacrificing our lives rather than taking them.
We ought to sacrifice our lives.
Judges 16
30 And Samson said, Let me die with the Philistines. And he bowed himself with [all his] might; and the house fell upon the lords, and upon all the people that [were] therein. So the dead which he slew at his death were more than [they] which he slew in his life.
We should be like Jesus.
Revelation 19
21 And the remnant were slain with the sword of him that sat upon the horse, which [sword] proceeded out of his mouth: and all the fowls were filled with their flesh.
Were the people of the Old Testament, David and Elisha and Samuel, supposed to not be like Jesus? Was it wrong for them to be like Jesus? No, rather, they were like Jesus.
Astronomer wrote:
Self defense, when it comes between me and the gunman, should always end with me laying down my arms.
A prayer for self defense would be, "It is written, God is a man of war. Blessed be God, who teacheth my hands to war and my fingers to fight." I pray that all men would yield to God teaching their hands to war.
Astronomer wrote:
If he is a non-Christian, then my first and foremost goal should be to bring him to Christ!
Precisely.
Psalms 83
17 Let them be confounded and troubled for ever; yea, let them be put to shame, and perish:
18 That [men] may know that thou, whose name alone [is] JEHOVAH, [art] the most high over all the earth. 
Astronomer wrote:
For I am his neighbor, and should have mercy upon his soul just as the Good Samaritan had mercy upon his enemy.
Luke 10
36 Which now of these three, thinkest thou, was neighbour unto him that fell among the thieves?
37 And he said, He that showed mercy on him. Then said Jesus unto him, Go, and do thou likewise.
The point was that the Jew was not the Samaritan's enemy, but his neighbour, rather than the other Jews, who did not shew mercy on him. The point was that it did not matter whether they were Jew or Samaritan, but rather whether they were righteous or wicked.
Deuteronomy 19
12 Then the elders of his city shall send and fetch him thence, and deliver him into the hand of the avenger of blood, that he may die.
13 Thine eye shall not pity him, but thou shalt put away [the guilt of] innocent blood from Israel, that it may go well with thee. 
Astronomer wrote:
If he kills me, then he kills me and I go to be with my savior.
And he will be that much farther from the Saviour.
Deuteronomy 13
10 And thou shalt stone him with stones, that he die; because he hath sought to thrust thee away from the LORD thy God, which brought thee out of the land of Egypt, from the house of bondage. 
11 And all Israel shall hear, and fear, and shall do no more any such wickedness as this is among you.
Psalms 78
34 When he slew them, then they sought him: and they returned and inquired early after God.
Astronomer wrote:
The world which John is referencing is not the literal world and the people in it (for then we would be disregarding scripture by loving one another or by loving our enemies) but rather than worldly lusts and wants. If you read the rest of that passage (16 For everything in the world—the lust of the flesh, the lust of the eyes, and the pride of life—comes not from the Father but from the world. 17 The world and its desires pass away, but whoever does the will of God lives forever.) He explains what he meant by the world.
 For all that [is] in the world, the lust... is not of the Father, but is of the world.
The lusts he speaks of are of the world, thus the world is that which lusts these lusts. That is why we should not love the world, for these evils are of the world.
1 John 5
19 [And] we know that we are of God, and the whole world lieth in wickedness. 
2 Chronicles 19
2 And Jehu the son of Hanani the seer went out to meet him, and said to king Jehoshaphat, Shouldest thou help the ungodly, and love them that hate the LORD? therefore [is] wrath upon thee from before the LORD. 
Astronomer wrote:
He's talking about the church! We, the body of Christ, are the temple of God!
It is true. But do you mean that each of us is not a temple of God? Only the Church as a whole?
1 Corinthians 6
19 What? know ye not that your body is the temple of the Holy Ghost [which is] in you, which ye have of God, and ye are not your own?
1 Corinthians 3
17 If any man defile the temple of God, him shall God destroy; for the temple of God is holy, which [temple] ye are. 
But what I argued from the verse was this: God will destroy that which defiles his temple, though his own temple is what he destroys. Some say that if it is wrong to destroy the Image of God in murder, then it is wrong to destroy it in punishment, and I was pointing out that God does this very thing.
Astronomer wrote:
How are we to love our enemies?
One thing that must be understood is that loving your enemies is not a new command. It is an Old Testament command that was written into the law:
Exodus 23
4 If thou meet thine enemy's ox or his ass going astray, thou shalt surely bring it back to him again. 
5 If thou see the ass of him that hateth thee lying under his burden, and wouldest forbear to help him, thou shalt surely help with him. 
An important thing to notice about the sermon on the mount is that at first Jesus quotes from the law and says, "Ye have heard that it hath been said by them of old time..." and in all these cases he expands on the principles of what is said: "...But I say unto you, That whosoever is angry with his brother without a cause shall be in danger of the judgment..."
But then he says, "Ye have heard that it hath been said..." not, "by them of old time," and then he contradicts rather than adds to what is said. The things that he contradicts the law also contradicts.
Proverbs 24
17 Rejoice not when thine enemy falleth, and let not thine heart be glad when he stumbleth: 
18 Lest the LORD see [it,] and it displease him, and he turn away his wrath from him.
We must love as God loves, not as sinners love. It is not of love to love  those that hate God, for God is love.
Astronomer wrote:
If God tells us to kill all those against him, then surely we aren't to love our enemies, but rather to punish them.
For one thing God does kill all those against him. But he has given us the responsibility to kill in punishment of certain sins, not all sins. If to punish wrongdoers is to not love your enemy, was it then wrong for the Old Testament saints to love their enemies?
Galatians 1
9 As we said before, so say I now again, If any [man] preach any other gospel unto you than that ye have received, let him be accursed.
Would this be to not love your enemy?
Does God not love his enemies when he casts them into the lake of fire?