Well, the truth is Strom Thurmond was very incapacitated and he continued to serve.
Just because someone has a stroke wouldn't disqualify them from serving, IMHO.
My dad had a stroke, he lost his speech, and use of one arm, but within a month, he was pretty much back to normal.
His speech came back a little slower than his physical abilities.
The question would be not one of physical limitations, but cognitive limitations.
Let us hope, he, like your dad can recover, and that his family does well.
My husband has had several strokes, caused by a hole in his heart which has been repaired, and he has no dysfunction of any kind. He was only in his mid-thirties when he had his first stroke.
Actually, I was thinking about Strom Thurmond when I made my "Week-end at Bernie's" comment. Do you remember how the Democrats treated poor old Strom when they wanted to keep the Senate in session all night for a filibuster and the Republicans asked if Strom could leave the floor? They said no.