I can't imagine what you are going through. Caring for my DH with dementia was the most difficult thing i have ever done. I think getting past infidelity in the midst of it would be unbearable.

It sounds like you haven't found anyone to share this with and that worries me. Carrying all that pain, anger... so many emotions... alone is not good for you. And you do need to think about you or you won't survive this caregiving journey.

Can you find a therapist you can talk to? It will be well worth it so you aren't carrying this burden alone.
Advice to just move on and think of him, while well meaning, is not helpful. Holding all of this is in is not healthy. It can come out in very negative ways, affecting your mental and physical health.

I pray you will find support through all of this.