I am new here but am going through similar feeling. W is having an affair with OM. When I first met the OM it was someone who was doing work for her and she was spending a lot of time there so I went by to check out the sitch. Met the guy and was totally put at ease. Not her type at all. Not educated. Not physically anywhere close to me. When I found out I was embarrased for her and for me, but mostly for her.
This is not about you.
You also mentioned erratic behavior. I would not overlook this. I have lived with this and have made excuses for it for 4.5 years in my relationship. It could be situational but most likely is not. He is probably aware of this too and has become very good at convincing other people that nothing is wrong and hiding it or is denying it.
Try to write down the symptoms you have witnessed and look up personality disorders. Someone just hit my sitch on the head today on this forum even though I knew my W had PTSD (at the very least) I made excuses for her behavior because of it. They have be to be treating it. Your H hasn't even admitted there is a problem.
I think it will go a long way toward explaining some of this stuff you seem to be having a problem accepting. I just went dark yesterday so I can't help you with that but it does feel better when you take control of your life.
My goal is to some day be the person my dog thinks I am
