I agree with H-B and Jitters. This seems like an abusive relationship and it would do you well to get out as soon as you are able. I know this is complicated by the kids, especially as one is so ill (I really hope the docs have figured out what's happening and she's on the mend).

Try taking a step back, looking at his behaviour over the past 25 years and thinking, do I really want another 25 years of this rubbish. You may have different opinions of when you got together but it we're talking a one month difference in 25 years! He needs to get over that. From what you say, you have been faithful to him in all that time (give or take a month). He is the one who has been unfaithful by texting/calling these 'work colleagues' and seeking comfort from their words rather than by talking to you about the issues. I'll give him the benefit of the doubt for the moment as to whether he's been physically unfaithful.

It looks like he doesn't see you as a partner in this relationship but as a nanny/maid. That's not a relationship and you can do better for yourself and for your kids.