I'm very sorry - your situation sounds miserable!
I just wanted to contribute my 2c (which might not be needed now, if the farm works out for you). I am in no means an UC expert, so please excuse anything I may suggest that is "off"
I think birthing at your home is not really an option. You're not going to want to be there with your ex - the stress and pain will not help your birth along! And it doesn't sound like kicking him out is really an option.
I really don't think trying to "sneakily" birth in your parents home is a great option either. They're bound to think something is up, and the whole worry (will they find out? are they going to burst in on you any minute? are you being too loud?) will also not give you a peaceful and calm environment!
I would discount the hotel room also - I can just see the staff or other guests calling the paramedics on you, and *that* would just spiral downward.... Besides I'm guessing it could just be kind of icky.
The cabin doesn't sound like a bad idea - but will you be able to keep it from your parents?
I really don't know if this is feasible, but coming to some kind of compromise with your parents could be the best option.
If the Farm doesn't work out (and obviously if it does this is all moot point) could you research the hospitals in your area? Maybe make a pact with your parents - you will tour the hospitals, if they will meet with the midwives/doulas who might be able to help you at home. Maybe you'd be able to work out a compromise you'd both be happy with? I think it would be wonderful if you could have a home birth with a midwife at your parents house - with a warm supportive environment and everyone happy
I do know a woman (who was happy with a hospital birth) who refused to see anyone but the nurse practioner at the DR office, and had her deliver the baby too.
Sorry - I realise all this hospital stuff is not what you were looking for, but I thought that researching your options might work, just in case you need them (depending on how other things work out).
If nothing else, some of the PP idea of transferring to the hospital later on sounds like it could work.
Oh, and I HEARTILY second all the people who advised you to see a lawyer!
Good luck, and I hope it works out for you.