I can understand where you are coming from. My mum was very ill for years with lupus, and wouldn't "allow" my dad to go anywhere, especially as her condition worsened. I could understand that she felt so completely dependant on him (as he was so good at caring for her, and took it all in his stride) that the thought of him not being there just in case she needed him was too much to contemplate.
I do feel bad for your dad, but I was forced to try to accept how much illness, pain and fear had changed my mum's personality. Her thinking didn't seem to be rational, and she couldn't accept logic- her thinking was right, and everything had to be her way, because she was ill. The worst example of this was my wedding. The whole thing was organised with all her needs as priority- the venue had to be local, we had to be able to bring a wheelchair, no steps, facilities for her to be able to go for a lie down if necessary, facilities for her to be able to have access to her oxygen, cars that she could access. I tried to get her involved with choosing flowers etc, but she sulked, because the attention was not directly on her. I paid to have her hair cut and took her shopping for a new outfit- which took longer than finding my wedding dress and cost far more!! I consulted her about the food, the band, but she was very cool about the whole thing.
On the day she was a nightmare. She insisted my dad be there constantly- she even interrupted my photos with him at home to insist he put a dirty cup in the sink! She refused to let him leave her side (I didn't even get a dance with him) and they left early at her insistence. I was very very hurt, but I had to just accept that the illness had changed her, and to understand that someone behaving so meanly is obviously not a happy soul.
She has been dad now for 6 years, and my dad is free to do all the things he couldn't for the last 20 years- he motorbikes, hillwalks, fishes, spends loads of time with his grandkids, has poker nights with his brothers (of whom my mum was thoroughly disapproving, for no rational reason!) I am please he is getting a chance to do all these things, but do you know, he just wishes she was still here, and would give it all up to have her back.
Such is the power of love, so cut your dad a little slack too for his apparent "weakness"