OP - you should be ashamed of yourself for being so disabilist. I’ve seen it before - people with disabilities of their own having no empathy or common sense with others who have a different disability.
As my user name implies, I have a lifetime’s worth of lived experience with being deaf and managed my own late father’s declining hearing and helped him adjust to his hearing aids. Which I did successfully without hectoring, badgering, shouting or holding boundaries! So here’s some sensible advice should you choose to take it:
Hearing aids are uncomfortable and take a lot of getting used to, both in their physical feel and the sound you experience through them - it’s not the same as your own physical hearing, so it’s hard to adjust and can often be a disappointing sound, even if it delivers results. They don’t restore hearing or give you back the hearing you’ve lost, they compensate by amplifying everything. It won’t be “like it used to be”.
That means the sounds you want to hear, like speech, are amplified, but so are the background sounds people with normal hearing can filter out. It takes mental effort to understand in that cacophony and is discouraging.
If he feels his ears are blocked, they’re probably not properly calibrated, leading to muffled sound. They may need reprogramming. This can be a matter of trial and error. Old people may not be able to articulate what the problem is, but these are common issues that discourage use of HAs - as well as feelings of pride and shame, and should be explored until he can put his finger on what it actually is.
Use these clues to find out what the issue with the aid is and see if you can get him further forward.
Don’t shout at him any more: this is RNID advice. It distorts your voice, distorts your lip patterns and strips your facial expression of appropriate context - you’ll look angry even when you’re not.
Face him so he can see your lips and expression. Don’t stand against the light - he won’t be able to see you. Stand with the light on your face instead. He’ll be searching your face and lips for clues even if he isn’t formally lipreading.
Use gesture - it’s not learning formal sign language but a PP described gesture like pointing to a keyhole as sign language. In reality that is natural appropriate gesture that adds context and aids understanding. It really helps.
If he doesn’t understand, don’t repeat things in the same words, try a different way of saying the same thing, eg substitute jacket for coat. Introduce the topic first so he can latch on - eg ‘for dinner - what would you like?’
Subs on the telly all the way - and are they big enough for him to see?
Go to the RNID website for more tips.