Legs, lungs, life. Can someone here please help my dad? (6 years of hell)

Hi. I'm writing as no more than a desperate cry for help at this point. My dad (61 years old) has been sick for 6 years. We've seen probably 40+ doctors and specialists, he's on a buttload of meds, he's done test after test and he's just getting worse. Nothing is helping, and even more important: NO ONE KNOWS WHAT'S WRONG WITH HIM!

Start of illness:

One morning six year ago I went up to my dad's place in the morning to have coffee. I found him sitting in a chair, out of breath, with chest pain. Ambulance was called (I assumed heart attack, so did they) and he was sent to the ER. No evidence of heart attack was found, no issue with the heart at all besides high blood pressure. And he never recovered. Everything has gradually become worse. Ever since that day he can barely walk, or breathe. His body just misfires in some way.

Continuation of illness:

He can't breathe properly. He does these exhalation tests both st home and at the doctors, and his numbers are abysmal. And ever slowly getting slightly worse. He's gotten a CPAP machine line 5 years ago and that makes it slightly easier at night, but not by much. Walking just a few steps is hard for him, and he has virtually no balance. He uses crutches and a walker depending on where he's going.

He can barely walk. He has trouble lifting his legs and his thighs especially aren't working. When he does a walking test (how far can you walk in 6 minutes) he's down to 20 meters, I think. Something like that. He needs to stop all the time. Yawns and breathes heavily even after a few steps. His legs also hurt A LOT, especially at night. And as I said, his balance is horrible. Dystrophy found in legs this year.

His nerves don't function properly. They done various neurological tests, abs the nerves in his legs abs feet aren't really responding. The response they do get is slow and weak.

He has terrible tremors. Specifically in his hands. They're minor or not there at all at rest, but even minimal effort (lifting a cup) causes severe tremors in both hands.

Hia blood pressure is weird. It differs from left to right and differs from minute to minute even at rest. I'm probably explaining it poorly but this is something at least one of his doctors has focused quite a bit on.

There are many other things as well, but these are the main ones, I think.

What doctors have done:

So, so many tests. Especially lungs. Multiple imaging done every year, shows nothing. Heart checked every year, nothing. Neurological tests on his legs as mentioned above. Testing for genetic disease, diabetes and COPD. Tests show nothing.

What they haven't done are imaging of head and spine, which I've been pushing for. But no response.

Probably unimportant info about patient:

61 years old. Swedish. Obese. Former smoker. Exposed to lots and lots of stuff like pain thinners and mineral turpentine (his father was a painter who did all of his art at the kitchen table all throughout my dads childhood). Non-drinker. Dementia and alzheimers in family but only (AFAIK) in heavy drinkers. His mother was in a gulag since childhood and most family members there were executed, so no real medical history there. He does suffer from bad headaches, but those have been a thing for a long, long time.

There are lots of things I haven't written and I don't have the exact meds they've put him on right now (mostly related to blood pressure). But I'll happily dig as best I can if anyone needs more info. I know this is a fairly unhinged post all over the place, but I hate what is happening to him.

And again: NONE of this existed before that morning when I found him. None at all. He had a fairly physical job and averaged between 15000-20000 steps a day. Was in good shape besides a moderately big gut. And then everything changed in a second. Walking, tremors, everything. Right at once.