How do you know when you cannot take care of someone any longer?

My wife had 2 strokes. 1 in Dec of 15, and another in the spring of 2016. She had 3 seizures, so 5 ER runs. She stayed in a home for 4 months and I've had her at home these 2 years. On top of it she has both apraxia and aphasia. The stroke took out her speech and right side. I obviously have to work. Thank God though as my 2 days off are awful taxing. I am wore down. I am exhausted. None of her family etc. has helped ... whatsoever. It's all me. I run a small business. I can't put her on Medicaid as from what I understand they could eventually assume my paid for home and business. My son is in it with me and I hoped to hand it to him. She is 56 and I am 53. Today is our 33rd anniversary and she doesn't know it. She has a lot of trouble comprehending. Dr's said she isn't going to get any better. We've have 5 different therapists of speech, physical and occupational therapy. No improvement since the first couple weeks. She's always had a temper and a short fuse and that's only inflamed more now with all this. I get through each day. But I am at a loss of what to do and wonder when my health will begin failing me as this is just utterly exhausting and she is just so rough to handle mentally. I feel so bad for and I have busted my ass trying to take care of her. I have to do 99% for her. I bathe, dress, undress her, you name it. I don't know. All I know is I am wondering if I've been running down a road I am just not capable of taking on. 2 years. 2 years facing I don't know ahead of me. Another 2, 5, 10 years of this? OMG, I can't imagine how I'd be able to last. I don't have anyone else to ask. Sorry for dumping, but I need some input and advice please.