I believe if you genuinely realized your own frailty and sins and genuinely prayed to God and acknowledged that he sent his one and only son Jesus Christ to die for your sins on the cross,who then resurrected (three days later), conquering the grave, and genuinely ask Jesus to come into your life to guide your future life, then you are a "Christian".
When you accept Jesus into your life, you are willing to put away your old sinful ways and start anew. You are willing to listen to God's guidance (Holy Spirit).
At the end of the day though, what you know as religion has nothing to do with your relationship with God. Only God knows that. The most "religious" person may end up going to hell because they didn't really give their life to Jesus. The most "corrupt" person may end up in heaven because they've got faith in Jesus.
Keep that in mind when I answer your questions:
1. Do you know why God doesn't want us to misuse his name? Why does he care what sounds our vocal chords make? The reason we shouldn't say "God" all the time, especially in trivial circumstances, is because it inherently puts less value to the word. It's like the word "the". We hear it all the time, so what? But God shouldn't be a "so what?" in your life. To avoid that, you want to refrain from misusing his name.
HOWEVER: If you, out of habit, say "Oh my God" in an "inappropriate" situation, don't beat yourself about it.
Remember that a person gives their life to Jesus out of thanks for salvation, not out of fear of judgement.
2. Look over the first paragraph. You can not miss a single service, and still not be a Christian. In fact, the strict "no missing church or you're going to hell" people seem to have put their faith in church, not in Jesus. However, going to church (provided there's a healthy church family, you never know nowadays) allows you to fellowship with other Christians. You can encourage each other. Give each other advice. I think God also likes it when people worship together. Why can't/won't you go to church now? If Jesus is first in your life, church should be an awesome place.
3. The old Christian cliche: What Would Jesus Do? When Jesus came to earth, he treated the "sinners" with respect. When the pharisees brought before him a lady who committed adultery, he did not stone her, but forgave her and asked her to leave her life of sin. It's good that you have nothing against homosexuals. No one should. They are a human being and a sinner like everyone else. However, just like you wouldn't promote husband and wives having affairs, I don't think we should promote homosexuality. Lust and homosexuality are "in our genes" but should be cast away in your new life with Jesus.
4. You can talk to God (pray) whenever you want. Being God, He's never too busy! The main thing to remember is that it's not the magic prayer. What matters most is what's in your heart, and no one can teach you that. Don't pray "the prayer" unless you genuinely feel moved and ready.
Here's website that may help:
http://www.everystudent.com/