You ask more than one question on this post, so let me see if I can address them all...
"With regards to homosexuality, abortions or for some religions pork, alcohol or pornography or a dozen other controversial issues that religions have, how do you know that this is what god wants?"
I believe that the Bible tells us what God wants. It's also important to note that Christians, while having the Old Covenant (the Old Testament) as our instructor on what sin is, we are bound by the New Covenant (the New Testament):
Luke 22:20
In the same way, after the supper he took the cup, saying, "This cup is the new covenant in my blood, which is poured out for you.
1 Corinthians 11:25
In the same way, after supper he took the cup, saying, "This cup is the new covenant in my blood; do this, whenever you drink it, in remembrance of me."
2 Corinthians 3:6
He has made us competent as ministers of a new covenant—not of the letter but of the Spirit; for the letter kills, but the Spirit gives life.
Hebrews 8:13
By calling this covenant "new," he has made the first one obsolete; and what is obsolete and aging will soon disappear.
Hebrews 9:15
For this reason Christ is the mediator of a new covenant, that those who are called may receive the promised eternal inheritance—now that he has died as a ransom to set them free from the sins committed under the first covenant.
Colossians 2 NIV
13 When you were dead in your sins and in the uncircumcision of your sinful nature,[a] God made you[b] alive with Christ. He forgave us all our sins,
14 having canceled the written code, with its regulations, that was against us and that stood opposed to us; he took it away, nailing it to the cross.
15 And having disarmed the powers and authorities, he made a public spectacle of them, triumphing over them by the cross.[c]
As Christians we still need to know what the Old Covenant teaches on what is sin because it's through the Law that we become conscious of what is truly right & what is truly wrong--what is sin. The Law condemns, but we have life thru Christ.
"You can claim it states so in your religious texts, but these texts have been translated and rewritten, added to and removed. how do you know that your specific denomination, or the belief's you follow were not added or altered by someone down the line?"
This is a fair question. I believe that we still do have originals of the texts used long ago. I believe that God used man to speak for Him, to commit His words to paper/papyrus/scrolls of leather to preserve those words forever thru the inspiration of the Holy Spirit. While we may not have the "first prints" per se, we do still have copies that were preserved over time. This has been a question that's been asked over again by people, but the reality is that we still do have the original texts preserved in this way--copies of copies so to speak. This is actually something that's not unique to the Bible's preservation, but also to the preservation of other ancient texts accepted as originals today (I also believe that just because someone claims to have written a Biblical text long ago as with some apocryphal writings, that doesn't mean it was intended to be part of the canon of Scripture: God inspires, & as such, He leads men to know His Word). What's generally sought after & examined is the agreement the documents have in transmission over time. Sometimes the agreement sought after in examining the past documents is also found in corroborating texts such as correspondence of long ago or sermons of that time that verify what was said as in quoting past texts. The texts as documented in other languages long ago also provide evidence for agreement such as Greek, Latin, Coptic, Syriac, Armenian, Georgian, & Ethiopic. If you've ever read Lee Strobel's THE CASE FOR CHRIST, you might get a better understanding of this (See Chapter 3: The Documentary Evidence for more...).
"how can religious institutions formed by men, beings with finite knowledge understand what an infinite being believes? it is simply beyond their understanding"
Romans 8:7
the sinful mind is hostile to God. It does not submit to God's law, nor can it do so.
Colossians 1:21
Once you were alienated from God and were enemies in your minds because of your evil behavior.
I believe that when people truly have a personal relationship with God, a spiritual transformation takes place from within that person affecting not only that person's life but the lives of others around him. It's kind of a ripple effect if you will. The Christian is part of the Body of Christ. Christ's Body on earth is not a church building, but rather, it is composed of all believers working together as one body in Him. We are enabled to do so in the power of God thru the Holy Spirit.
Romans 12 NIV
http://www.biblegateway.com/passage/?search=Romans+12&version=NIV
1 Therefore, I urge you, brothers, in view of God's mercy, to offer you