I was amazed to find a community like this, there seems to be somewhere for everyone

To the point, I'm 18 years old and while I don't suffer from any problems personnaly my dad does. He's 56 and had, well some kind of nervous breakdown. He doesn't eat, wen he does he throws it back up. he's been forced to retire from his highly stressful job, which he hates as he's passionatly independant.
It's been around 3/4 months now since it all began. He has had two epileptic seisures, i think both were ionic clonic, not sure though.
i was the one who found himm on the kitchen floor and had no idea what to do. Hospital said nothing was wrong with him and sent us home. He suffers from hyper sensitivity from sound, light, pretty much anything. the hospital are still pending an MRI on his head to see if theres something wrong. It's been 3 months now.
Hes been through numerous physchologics, all of them are jrs who leave in 4 weeks anyways.
Thats a brief outline i guess.
My point of this is that, its come to the point where i feel completly drained. i just cant stand listening to him wretch up nothing but bile. watching him be too weak that hes falling over whilst refusing to go to hospitals and meetings, refusing to take his medication because it throws his body all over the place.
he acts like an 8-yr-old. One minute hes my dad the next he just refuses to admit somethings wrong and gets all childish.
All this just makes me wish, as unbelievably harsh as it is, that he'd just die. its currently 5.30am and ive been trying to drown out the wretching noises for ova 4 hours now.
I'm sorry this is so long. No idea if anyone will even bother to read this far. its just so complicated that it takes so long for someone to really understand. He just doesnt want to help himself. im sure he wouldnt care if i came home one day to find him crouched over the toilet dead.
I'm on my last legs now, everyone we ask for help he either pushes away or they just look at him as another person or another patient out of thousands. nothing gets done. and i dont care to try anymore because i know that dad wont try for himself.
fine if he wants to rot away in a messy house full of cat $#%^ and dead mice, but i still want to help him so i stay n watch him wretch n try to do something to help.
Would it b so cruel just to leave and never look back? i just want a normal family that doesnt walk into my room at night because he has no idea what hes doing. i feel so trapped.
is there anything anyone can suggest, because im all ears.
Thank you for reading this, sorry its so long. and probably off the point. i hope i posted it right and in the right area. sorry if it isn't.