I am going to give you a slightly different take on this - just for arguments sake.
You will find threads on here from people who have not exposed the A....generally after a while they move into the MLC forums or sometimes they stay long term in infidelity, (more often than not they eventually move though). They also end up in the D'd section.
More than once I have seen people say after a year or so that they are fed up of their S cake eating. The LBS acts all nice and the WAS just walks all over them. Do you want that?
If you GAL etc and wait, even if your H comes back what is the incentive for him not to do the same again at some time to manipulate you into you acting how he wants?
OK, I am playing Devil's advocate here to some extent. However, think about what would be 180's for you. I think I remember you saying in an earlier post you both led active lives and did your own things. Do you think there's a chance your H felt you didn't need him? Do you think he needs to see you putting up a fight for him? if so, how is the best way you can do that? I am not saying exposing the A is the best thing....but what would be?
Look at 180's....and only do them if you are comfortable with them-otherwise they will not stick. They have to be things you believe need altering; things that you can see weren't quite right. Don't do things out of malice...like exposing the A....only do it for a positive reason. If you are not sure on a plan of action invoke the 48hr rule and do nothing for that period of time while you think about it.
There are reasons for outing an A. Firstly you stop the secrecy which an A often flourishes in and which makes it seem exciting as opposed to seedy. Secondly you can get support from others around you. Thirdly, you stop your H playing the separated card for a while which enables him later to move on without it being obvious he was cheating, so as to lower blame of him in the eyes of others, (walking out on someone with such a young child is pretty low).
Down side is mainly that you can't control the fall out and once done you can't take it back. The week after I exposed was absolutely awful - really extreme. However...when I compare my situation now I am further on than many that discovered their S was cheating at the same time I did. I guess I would liken it to ripping off a plaster....I did it quickly and got the pain out of the way in one big swoop....rather than slowly soaking it off and wondering what the wound was going to look like when I eventually got there. I got to see my wound sooner and let the air get to it earlier. It hurt really badly but it healed quicker.
No-one can tell you what to do. You can read about people's situations but at the end of the day only you REALLY know your circumstances.
Personally, I couldn't sit there and play nicey wifey while my H sat and tried to decide who he wanted to be with. He asked me to do that. I ended up nearly killing myself and after talking with a psychiatrist with me my H knew he had to make a decision.
BTW, maybe it would be enough just to let OW know you know. Once the OW in my sitch knew I knew she no longer would accept my H going between the two of us - she also pushed for a decision....just as the psychiatrist said she would. It was her undoing - she was not suitable and my H was just not ready for that pressure from her.
I apologise for the long post, but I also note you had IVF. Have you ever had any C for having to go through that? It often causes rifts between partners as it is such an emotional and financial roller coaster. It could be at the route of some of your H's problems.It changes priorities in a R without partners knowing sometimes and oft a man can feel like he is just a donor rather than a lover.
just some alternative points
Saffie me 46 H 46 M in 1986 D20,D18,S16,D13 H's A 01/05 to 07/06 H recommitted to M 07/06 renewed vows 09/06 Going from strength to strength