Whether he loves you, or he loves the situation, or he just loves the shag and the ego boost are all entirely possible but this is neither here nor there. He might be a one-off cheater or a serial cheater, both exist. That is also neither here nor there. A one off cheater is no more ‘noble’ than a serial cheater. You don’t know for sure that although you might the first, you are definitely his last. You might actually be, but again, this is pretty irrelevant.
The ongoing hurt must be unbearable, agreed, but the bald truth is that the situation will go on and on, with no sign of him making his mind up about anything, until he has to. Why would he, whilst his poor wife is in the dark and you make yourself available to him whenever he wants? Why upset his wife and family when he can just carry on doing this anyway with no fallout or consequences to himself?
Neither his wife (because I presume she doesn’t know) nor you, have given him any ultimatum or impetus to change his behaviour or make a decision. He has no motive to do so himself, however much he may or may not love you, his fantasy future at present doesn’t appear to include an exclusive life with you.
So do you carry on hurting and wanting and waiting, letting him do whatever he wants, with scant regard for what you want, or do you save yourself and your mental health?
You know that you need to clearly tell him you can’t carry on like this, that it’s over, then cut all contact you can in the difficult circumstances. Limit communication to as little as possible, and no communication about anything not work-related. You know this has to happen. But you’re not yet doing it.
So, the simpler question to ask yourself is “Do I really want to move on?” You have said it goes against your own moral code, that you know how terrible it is etc, but this hasn’t motivated you to stop. These are your choices, this is not coercion or a literal inability to stop. You are choosing to carry on.
Instead of choosing to continue, giving you more long term pain, you could choose to stop, painful in the short term but better for your self esteem and mental health long term. All the advice in the world, kind or unkind, won’t stop you or give you a way out until you listen to the advice and choose to do so.
Until you really honestly do, you will carry on suffering and hand-wringing whilst he does what he likes, for as long as you let him, or until he gets bored, or until his wife finds out. He won’t decide, you need to decide for yourself how you want your future to look. Tough decision, but if you are posting on here you have clearly moved nearer to a place where you take back control of your life and stop letting circumstances (and him) dictate.
I hope you make the best decision for you, OP. Take care. X