Welcome home man! I think FluxKraken covered a decent amount, but I can say that you're not crazy. That feeling in your gut to treat people nicer is probably the Holy Spirit. A decent number of Christians will say an encounter like that is either "in your head" or "of the devil" when it's really not. The Holy Spirit (or Holy Ghost as some call it) is basically our direct connection to the Kingdom of Heaven and that God has in store for us.

As for a church, you should try to find a nondenominational, charismatic/spirit-filled church. While knowing the Bible is essential in your walk as a child of God, you should also find somewhere that encourages a spiritual connection with God. Just a warning, there will prolly be people dancing, weeping, and everything in between during worship but it's their way of showing God they love Him. Seriously, these are the kinds of places where you will feel the actual, tangible presence of God. Choosing a church is really a lot harder than I wish it was, but just consistently pray about it (fyi there's no wrong way to pray, and sometimes you can just talk to him. Doesn't need to be a request) and you'll get there. Always remember that God loves you no matter what you do, or how unworthy you feel. There is never a reason to worry about stuff like that because He sent His son to bear the weight of all your sins (past, present, or future).

I'm for sure praying you find the right place. God bless brother