I Think My Kitten Has Cerebellar Hypoplasia

I have a 6-week old foster kitten. He is from a litter of four, with two
dying at birth, and one dying about one day old. He is the sole survivor.

I've been increasingly worried about his motor skills. At 4-5 weeks I
expected to see him grow stronger, and by week 6, stable on his feet.
Instead, he seems to have plateaued at around week 4 - falls over all
the time, can't coordinate. Can't really use the litter box, because he
cannot hold himself up. He's started trembling, especially after eating.
At first I thought he was straining to make a bowel movement, but after
researching I think it is another symptom of Cerebellar Hyperplasia. I
viewed a few videos on youTube of cats with this disorder, and I am
pretty sure now it is what he has.

So - what do others here know about the disorder? I've googled around,
and see that cats can live a long, pain-free life with the disorder. I
am fostering him from our shelter, so IDK if they'll want to put him
down. I'm trying to get as much info I can right now to determine if I
should fight to keep him alive, get him adopted, or if I should let him
be put down (he belongs to the shelter, not to me).

Thanks in advance.