hearing aid(s) for the first time are kind of like this, it does take quite a bit to get used to using the aids, etc. A whole new lifestyle actually, where you sit in a room in relationship to others in the room so you can follow conversations, where you sit to favor your good side (the side the hearing aid (HA) is on), handling and dealing w/ the other noise/feedback in the room, etc. I've worn HAs for about 55 years now, and it is still a challenge to use them. One particular problem is that folks don't really realize that one is using the HAs until they happen to glance at your ears, etc.
Best wishes to you and your dad, at least he's farther ahead in dealing w/ getting a HA finally, I hounded my dad to get himself some/or a minimum of one HA, wouldn't. I even gave him two of my older ones and told him that I would pay to get new ear molds and recondition the aids. No luck. People get set in their ways.
A shame really, being that the solution is so simple.