What I have yet to comprehend is at what point does what they say and what they do become allowed to be taken in fully and believed as true emotion? Once I start believing nothing they say, how do I decide to again believe them?
At some point they MAY begin to make comments about wanting to work on the relationship. That's when you look at their actions and see if what they're saying goes along with what they're doing.
For instance, if there was an A and they said they wanted to make the M work, but wont break off contact with the AP, then its likely not real.
However, the time now isn't to focus and look for that happening. You would be gaining expectations and trying to look for those things happening. You are going to be so desperate to see those things happen you will almost make them up from nothing at all.
You need to focus on yourself and try to start making changes that better your life.
Accept what is, let go of what was, and have faith in what will be