Homelessness is a last resort.
If you have a roof over your head, and if you're physically safe there, then stay until you're better prepared to leave. I know, I know, it's so hard to hide the trans stuff, but provided you're not at risk of self-harm because you're repressing your gender identity, then I can't urge you strongly enough to wait.
It's not a perfect situation, but if you're homeless, jobless, insuranceless, you'll find it a thousand times more difficult to transition. Being homeless is unpleasant, often dangerous, and generally a stressful and miserable way to live your life.
When you turn 18, you're in charge of your own medical care. You control your own therapy, your own medications, the whole lot, and your parents don't need to know.
Please, think about this long and hard. Running away should be a last resort. Leaving home without a means to support yourself is also inadvisable.
Sorry to not be able to offer you a solution to your horrible situation, but don't make it worse. Transition isn't a race, and most of us can keep our feelings inside for just that little bit longer (or find ways to work around them in private) until we're able to branch out on our own.
Best wishes.