I tend to be quite balanced when I approach matters, so often my thoughts, actions and opinions are not at either extreme, and the stuff I do might seem to be a cop out rather than a definitive action. But I find that my methods have served me fairly well.
We are all growing older. There will always be younger people recruited into our workplace. They have energy, brightness. enthusiasm, so many of them will be a breath of fresh air. We can’t get rid of them and we can’t ignore them either.
While I don’t think digging and baiting are reasonable things to do in a normal relationship, I do think paying careful attention and some checking up can be considered due diligence. If I find something that I can deal with before it becomes a huge problem, then it’s a bonus. If I don’t find anything, then I’ll check back again after some time, as part of maintenance. I don’t think I would be offended if my OH checks up on me because I have nothing to hide, so I actually wouldn’t feel put out by the checking.
If I found something like platonic messages with a very attractive and endearing younger colleague who has potential to derail my life, I would be watching much more closely. However I would not wait to catch him red-handed unless I wanted to end the marriage deliberately. Instead, if I had the luxury of some time, I would create situations to remind him of what he has / make him consider his options eg make up story about a colleague falling for someone at work and how much mess it is causing for his/ her reputation and family life etc, stuff that can pass off as idle chat, but might jolt OH into considering his own position if it strikes a chord.
It is possible to mention that he’s been calling out names in his sleep - if I used a furious jealous tone he’d probably more defensive and non-cooperative, but if I bring it up with concern eg ‘I heard you calling out the names of a few of your colleagues and maybe one or two names I don’t recognise... is this related to a stressful case you’re dealing with / have they caused some difficulties at work, and would it help to talk about these?’
It would be easier not to say anything at all while you decide how to proceed, but if your close family are picking up on you being different, you might want to find a good reason for being so off-colour. Don’t let the status quo drag on for too long lest you become known as moody grumpy non-communicative wife at home.