For a cheating spouse to accuse a betrayed spouse of cheating is purely SCRIPT. It happens, I'd estimate, 50-60% of the time. Don't dignify it with a response, other than to say ONCE "I take my marriage vows seriously, and I would never do that. Now please don't bring it up again."
In fact, I think the place where you're largely getting "stuck" here is that you do indulge her far too much on her "rants." Most of the conversations and interactions you describe with your wife go on FAR too long, in my opinion. A simple "I'm sorry you feel that way, I need to go thus-and-such (GAL activity)" and be DONE with it would be a far better approach.
Having marital arguments in front of the kids, particularly, is a problem. When she starts this, you need to cut her off with a polite -- but firm -- "This is not appropriate to discuss this in front of the children. Let's talk about this later" and STICK to it.
I think you're looking for some deep philosophical insight from the rest of us as to what's going on with these interactions (ex.: "Why does she care if I'm seeing anyone, when she's done this to me?"; "why is she like this?"), when in reality all you have is simple BUTTON-PUSHING with the former, and "why she is like this" on the latter is, "she's in walkaway mode, and this is what walkaways do."
You're still WAY too reactive. Your immediate goal should be practice not being REACTIVE. Picture her down in a pit, full of all kinds of beasty nasties, and tell yourself "Mark, don't jump into her pit with her. It's a cheeseless tunnel -- DON'T ENGAGE."
OK, so I just mixed my "pits" and "tunnels" analogies, but you get the point. Do you think you could try this this week?
