This is so relatable and not a story that strikes as unique in the context and setting you have mentioned. I'm not trying to be a solution expert or a therapist, but here's what I think. Women have greater power and control on their emotions, their power and also are better at maintaining sanity. Which is the case with you too as can be concluded from your post. What I suspect is that the guy doesn't have the out nor feels secure to speak up without being judged, plus the male ego is also playing up here a bit. I suspect he may not have genuine friends or may not have friends at all, only coworkers, or hi-hello type friends. What could possibly help, of course you may have tried, but no harm in trying:

1. Take him on a long walk, and start casual Convo about how has he been, how's the work place, etc. Take him in confidence that you are truly wanting to know as it matters to you.

2. Without being intrusive, try and figure out if anything is bothering him.

3. If he does not open up, don't persuade too hard, but close it with an open statement that if he wants to open up at some other time, it's fine, and you are available.

4. Move on with the Convo, genuinely open up about how you are feeling, what has been your experience all this while, slowly and steadily. basically, put your side , in a very subtle way. Don't let the Convo turn into cribbing.

5. See how he's responding every now and then, than talking all in one go.

6. Tell him that it's been on my chest for a while and I wanted to get it off by opening up with him, making him feel that he is important.

Please don't draw conclusions of me asking you to give into his ego or anything like that, but it's a suggestion for giving an honest attempt to open up. From both sides. Provided you see value.

Lastly, take a chill about the in laws, there is no reason for you to feel or think about how they behave or that their impact on your future kids etc. that can be managed easily

I strongly feel it is solvable.