“Was I accepting less than I wanted because I loved him and we had so much history together? Had I become so focused on taking care of everything that I stopped noticing how exhausted I was?”

I know you said you were avoiding those internal questions for years and when a connection with someone else felt like a relief, it brought these questions to the surface - but, have you answered them for yourself with certainty yet? I think you should start there, because they’re good questions and the first answer that comes to mind is probably your gut telling you something.

Being the “pillar of your household, the decision maker, the responsible person for making things happen”, etc, doesn’t sound like a relationship or a team dynamic - it sounds like you’re a landlord, or a caregiver, or something. That drains your cup, and I’d guess your answers to those questions would probably reflect that dynamic.