There's some serious problem with what you have just described to me. It sounds like he doesn't understand that first of all there is a division between the Old Covenant and the New Covenant. When Christ fulfilled all of the prophets and Law the Old Covenant was done away with and the New was put in place. This takes care of many problems. Nowhere in the New Covenant is the command to tithe given - nowhere is there any command of "seeding" for anything. I would like him to show from the Bible that what he is teaching is true, and if I were you this is what I would ask him to do.
Also, I think it's important for you to understand that God does not call us to a church. You might think that particular group is where you are supposed to be, probably because your girlfriend goes there, but I don't believe that you, or anyone for that matter, has been "called" to a particular group. It sounds to me like you really don't feel like you belong there anyway.
The first thing that you should do is get your Bible, find out where the Bible contradicts the things that your preacher is preaching. Confront him with the word of God. If that doesn't work then you need to take another person with you and show him why you believe that he is wrong. If that doesn't work then you need to consult the elders. If that doesn't work, then you have tried to share the truth, and it's time to leave.