Actually, even as a child you have more rights then you are led to believe. You could even make an anonymous call to social services in your area and tell them that you feel threatened. I know that seems extreme but you will be eighteen soon and you may be able (forced even) to talk to a counselor who could help you with resources.
I found this article that deals with your situation. Parents have a legal obligation to support you. Threatening you is not support.
Read the items under "Homeless" because they list a lot of resources that you might be unaware of. You could even tell your boss that you are worried that you won't have a home soon. They might be able to help you find help in your area.
You have options and resources. You feel stuck and alone because you have been told that you are stuck and alone.
My parents did some similar stuff to me when I was younger. I actually asked if I could move out at 17 and they said no and I believed them. I could have had resources if I had just told anyone outside the religion and my family what I was going through. I actually did attempt suicide. I don't advocate it. But it did teach me some valuable lessons. As long as you are alive, things can get better. They don't always get easier because life is hard, but you learn how to deal with stuff and that makes life better.
Getting exercise, sleep, and a good diet is imperative to getting out of depression. If it's too hot outside, clean your house. Seriously! It is good exercise, it is something small that you can accomplish and feel good about, and it is easier to deal with the stuff going on in your head when your house is clean. It is also a symptom of depression to let cleaning slide which just adds to the pressure of the depression. I don't mean clean the whole house... that can feel overwhelming and then you feel guilty if you can't get it all done. Pick an area and clean it. The area can be small. Then, when you feel ready, pick another area and clean that.
There is a book you should be able to get from your local library called 'Clearing Your Clutter with Feng Shui'. I know, it sounds flacky. The thing is that it goes into some of the symptoms and behaviors of depression. Not what you would expect from the title! It is a great book and one I keep around for those times when depression is looming above me.
You can also get access to resources for getting a place on your own at your local library. Getting a plan of action for yourself will help you both practically, and also help you to feel like you have some control which will help to ease the depression. Take a gander at Craigslist in your area, or in the area you want to live in. There are often people letting rooms at low cost. You can get a good situations which will allow you to get out of your parents home while at the same time allow you to save some money and plan for the future. This isn't to say that you need to leave your home right now, but it will help you plan for when the time comes... if worst comes to worst.
Also, ask your local librarian about community colleges in the area. Community colleges are much easier to get into then bigger colleges and you can easily transfer from one to a bigger university later on. I don't know your situation, but the kids I knew who did home-schooling had a harder time going to college afterwards. Concentrate on getting an education which will help you no matter what you decide to do later in life, or even no matter what the future brings. Going to college can seem daunting and overwhelming, so don't think of it like that. Instead just take a look at what your options are. It doesn't hurt to look. And if your parents don't like it you might consider reminding them that the people who have the best jobs and help out the most at Bethel also have college degrees. The organization has lawyers, all volunteers who went to college against the advice of the organization. All those people doing the advertising and production and acting for the new digital media they do... well that takes an education, one you wont get just by going out in service. There are lots of ways to serve the organization and you should be able to choose a way that you can be happy with. I'm not saying you have to stay in the organization, but that you have options no matter what life choices you make. College gives you even more life choices.
Also, a few little tricks. Wake up, look in the mirror, smile at yourself, and say, "I deserve to be happy", and then smile again. What makes you happy is up to you. But you do deserve to be happy. This is an affirmation. Say it long enough and you will believe it. Smile when you do it and you might actually feel a little bit happier than you were before you said it. Eat a piece of chocolate (not a whole cake or anything) when you are feeling low. Physiologically chocolate releases chemicals in your brain which tells you that you are feeling 'in love' which is a great feeling, while the act of smiling releases chemicals in your brain that tells you that you are feeling 'happy'. These little tricks won't cure your depression but they will help. Smile before you exercise too. It will help you feel like you are doing the right thing, which you are... but sometimes the right thing for our bodies doesn't actually feel right and good.