Your family have alot to bear at the moment. I think yes while we should all be thankful for modern medicine and be grateful with all advances in technology etc, sometimes we are still in need of venting, being upset, mourning the life we had etc etc. It's OK to feel all these things especially if like in your situation it also means a loss of communication

If you and your dad use sign, can you start learning sign for deaf/blind, from my understanding with the sign language I know it is still the same but with one person cupping the hard of the other and reading the conversation through touch. If he doesn't loose his sight, no harm and another skill honed.

You are concerned about his hobbies could you both in some way find a way to adjust the hobbies if needs be?

I'm happy that the thoughts of your mom loosing her sight doesn't seem to be a big worry