You've done the right thing by going to therapy and solidifying your own relationship with each other. So I think you should be heartened by that. You've set boundaries together, and you are taking some baby steps. That's smart. They're not screaming or making demands. That progress! If the in-laws overstep their bounds, your husband (not you) should tell them to back off. So take heart that you have made progress here!
Maybe they hate you, maybe they don't. Maybe they are totally useless at relationships and will never be able to more than they are doing now - BUT there has been a definite reduction in hostilities so that is terrific. Getting a comment about the weather is a VICTORY - try to see it that way! It's innocuous, it's not confrontational, it's not controversial! They aren't criticizing you or picking a fight! Keep working with your therapist until you can see this as a positive step.
The problem is that you are "starting to get resentful" - so you are changing now, and developing a new kind of animus that's not based on their prior offenses but based on - what? - some frustration that they aren't even better? Maybe you can get to the point of treating them as people with a disability - a social disability - who cannot do better than they are doing. If your husband wants to hope for more, as if somehow middle-aged people are going to change their personalities more than this, that's something he should work on in therapy as well. The more he hopes for pie in the sky and the more you are resentful and not wanting to fake the small talk, the great division there will be in your marriage. That's the exact opposite of what you've worked on for 3 years! So, you make small talk all day long with everyone else, right? We all do. We chat with the checkout cashier and the boss and the person in the other work department we don't really like, but we do it for harmony in a situation that is tough to avoid. It's not substantive, but it's harmless, and it really doesn't take all that much out of our day.
Your only other option is to never see them - and I think that builds up more stress in trying to avoid them and make excuses. If your husband wants to see them on his own, great. But have him visit for "no reason" and not just on major holidays or birthdays where he has to make up some reason why you're not there. I don't know how close they live, but if they're nearby and he sees them once a month and you see them every 2-3 months, is that doable?
I think your couples therapy isn't done if you are still not on the same page, and if he is wishing for major changes and you are seeing increasing resentment and a desire to pretty much break off contact. There's no right answer here - but if you two aren't together on it, then it's the wrong choice.
Good luck.