17 Year old son has rare condition causing stroke

My 17 year old son had a stroke, due to a rare Juvenile Vasculitis disease.  I came home one day after work and found him lying in the bath tub, he was fighting for his life.  He was med flighted to Children's Hospital in Knoxville, where they then confirmed his diagnosis after many test.  He spent 4 days in ICU, where he struggled for his life.  They confirmed he had a 95% blockage behind his right eye, and began him on steroids and blood thinners.  Now with this condition they stated that they had not seen a case there in over 15 years.  So I then asked what are the odds of him having more problems, they stated that he will either never have another problem again or he will begin to get worse.  So from that point we spend almost 2 weeks in the hospital, they then felt comfortable enough to let him go home.  Once we get home for the first couple of months commuting our 2 hours to Knoxville going to the doctors at least twice a month it seemed as if everything was getting better, but then things begin to take a turn for the worse.  They have now found he has another blockage in his left arm, they stated that he has a 8 second delay for his blood flow and this was in January.   So we went back for additional tests and a second opinion, they then confirmed that the medication is not working like they had hoped.  So they sat us down and told us with how he is progressing he would be lucky to survive another year. So we sat down together and I explained to him the situation.  He then went back to the doctor again in February, they again had more bad news for us after more test results came back.  They then told us that he now had a 12 second delay in his blood flow to his wrist, so within a month he had lost 4 seconds, he also has another blockage forming in his left leg.  With that being said they said that he will be lucky to make it 6 more months if it begins to progress at this rate.  He has almost daily nose bleeds sometimes lasting up to 6 1/2 hours, his legs swell to where he is unable to get out of bed, and he has gained over 70 lbs since all this begin because he was taking 60 mg of steroids a day.  So with all of the weight gain and steroids he is unable to intake his sugar correctly through his muscles so its coming out through his skin causing a very dark discoloration all over his body.  So since all this he was lucky to make it to school 1 day a week, so he actually had to drop out of school, because he was unable to keep up with his work and continue to go on a daily basis.  The reason that we are asking for help is he has occurred $704,000,00 in medical bills during this time, (and are continuing to build up more with each visit), we requested TN Care to assist us with the bills but they say that I make a little to much money to get assistance.  I am a single mother of 2 and I work hard everyday. However, I do have to pay for his prescriptions also out of pocket along with a new diet that was specified for him.  I make payments every paycheck to each doctor, radiology, med flight, among many more, but it is getting very overwhelming, because that is on top of our normal bills.   I am just trying to keep him comfortable, and spend as much time as I can with him, because it may be our last day together and it would be a blessing if we could get any help at all.  Thank you so much for reading our story.