I've never considered myself as a doormat. Quite the opposite. But for some reason, when ds1 was born I simply assumed that (ex)DH would be as pleased as me to move into a new phase of our life as parents. One that didn't involve seven nights a week at the pub. In fairness, I never had any cause to distrust his fidelity and the pub going was a social thing rather than a hard drinking activity since we'd both been keen members of various sporting things attached to our local. But for all that, I assumed we would certainly cut down on the constant "outs" and enjoy the company of friends rather differently.
Now I'm not keen on laying down laws within relationships because it shouldn't be necessary. You are, after all, both supposed to be adults and theoretically able to tell the difference between appropriate and inappropriate behaviour. However, this is one area where I now realise I shouldn't have made assumptions and instead, from the outset, I ought to have simply said it wasn't acceptable for my ex to carry on as before. Because once the habit had been established it was even harder to break and ultimately, 6 years and another child later, I left him.
We didn't have grandparents who lived near enough to act as regular babysitters but I can see why the OP's ILs would now feel deprived of the seeing their grandchildren if they used to have them to stay so regularly. To be blunt, they must feel very used.
So no, OP, YANBU in being pissed off at your husband's behaviour - the episode when you were discharged early from hospital is shameful - but be prepared that, 3 years on, it's far harder to break previously accepted habits. Convincing him that his behaviour is inappropriate for a married man with children could be very difficult.