My Mum had this - swollen ankles and legs, hospitalisations for breathing problems. She was younger than your Dad but had Type II diabetes and was very overweight.
What happened with her, and I think it's not unusual... something, often an infection, would trigger breathing problems and she'd be put on diuretics and often hauled into hospital for a week or so. Then they'd buff her up and she'd be out again.
The local heart nurse would visit her at home and helped keep her out of hospital as much as possible.
The leg swelling ended up with diabetic leg ulcers which had to be redressed all the time - district nurse and GP surgery nurse helped with that. An attempt to sort the ulcers with compression bandages backfired as it shifted the fluid to her lungs.
The last two months of her life were in hospital where they tried to treat the infections, keep her heart and lungs going BUT the diuretics buggered her kidneys in the end. Failing kidneys result in problems with electrolyte balance which result in the heart not beating as it should and in the end her heart stopped.
I had worried that breathing issues would be the end which is not a nice way to go but that didn't happen.
Um practical advice?
Having healthcare LPA was helpful in getting people to talk to us. Get that sorted if you can.
She had an Advanced Care Directive done and we were instructed to be heavy on quality of life. That might not matter so much when healthcare resources are really stretched like now but in quieter times...
The heart nurse was great - see if your healthcare lot offers similar.
You can have home oxygen set up (and Mum did have this very briefly).
If he's on diuretics at home make sure he has a bedpan or bottle close so he doesn't have to worry about getting to the loo (advantage of being a man).
Spend time with him - at least the little comforts and the company will help. Have the conversations you need to have, bring out the old photos, get the stories told, tell h your plans for the future, and have no shame about feeding him a diet of cream cakes and amusing kitten videos if that helps at all.
It was a few years of bouncing in and out of hospital - 2-3 - but she was younger (and no covid-19).
Hope that helped a bit. I remember how at sea I was.