Just remember that turning 18 doesn't mean you can do anything you want to. As long as you live with your parents there will be rules as there should be. Rules help bring structure to your life whether you like it or not. You have a whole life ahead of you to decide if religion is going to be part of it or not.
Like some of the others said you just have to suck it up and bear with it while you are still living at home. Once you are on your own you can do things your way but even then you will have rules and laws that regulate what you can and can't do. Trust me, when you get out on your own there will be many things that you won't like or find annoying but you won't have a choice about. Life is not fair but you have to make the best of what you have.
As for losing your snakes, that is just their way of getting you to follow the rules. Years ago people would take a belt to your butt to do the same thing.
At any rate once you're out on your own you can go to church if you want to or stay at home and do other things. Of course you'll have to find a place that will allow you to have snakes as some places have rules against them. There are compromises to be made in everything you do in life so you better get used to it.
As some of the others said talk with your parents in a civil way and let them know your feelings. If you discuss it with them in an adult manner maybe they will understand your point of view and you all can come to a good comprise that everyone will be happy with.
I am not saying you have to follow their religious beliefs but you do have to follow their rules as long as you are in their home. You can believe any way you want to, that's up to you.
Okay my rant is over I just wanted to put my two cents worth in. Whatever happens I hope it works out for you. Good luck.