Hi OntheGallow, here are your questions as I understand them,
1) Why does the God of the Old Testament not seem match up with the God of the New Testament? Answer, the New Covenant is superior to the Old Covenant. But under either Covenant, a person could obtain approval through devoted faith in God. Hebrews chapter 11 lays that all out.
2) Jesus did not come to abolish the law, so why don't those commands in the Old Covenant still apply? The Old Covenant was "fulfilled" by the New Covenant, so only those portions of the Old Covenant that are endorsed in the New Covenant are still requirements.
3) How would they know they were virgins. I do not know, the Bible does not say. I would guess maidens under a certain again would be assumed to be virgins because of the cultural norms of the day, but that is my guess.
4) Because God ordered the killing of babies, that seems to disqualify Him for worship. Again, God has the right of the potter to mush the clay. To say He is not doing what He should is to judge Him as if He were a man, operating under our rules.
5) Why is God worthy of worship? The Bible tells us the attributes of God, like Holy - does not sin, like Just - punishes people according to their knowledge, Merciful - gives mercy to those who love Christ with all their heart, Keeps His promises - He will do what the Bible says He will do. So the issue is, are we worthy of worship, or rather than extolling our virtues, should we extol the virtues of unconditional love, perfect justice, and divine mercy.
6) Why does God allow us to live in the corrupt world where we are predisposed to sin, and then suffer the consequences? Another way to say it is why does God not take away our choices to do other than what God desires? When we repent, we bring glory to God. This would not be true if we did not make that choice, but could only do what God desires. Thus, in order to fulfill our purpose of creation, which is to glorify God, we must have the capacity to trust in God or not.