Hey mtmomma!
Welcome to our Mattress Forum 
Well I can see why you’re feeling stuck! You’ve been through a few very different mattress experiences, and it sounds like none of them have really solved the mix of comfort and support you and your husband need.
With your husband being taller and heavier and you being more petite (and dealing with hip pain), the challenge is finding something that balances pressure relief with good alignment for both of you (especially if you’re not looking at split configurations).
Lower back and hip issues usually come down to how the comfort and support layers are working together. If the comfort layers are too thick/soft, the pelvis can sink too far and throw off spinal alignment. If they’re too firm, the hips and shoulders don’t sink in enough, which can leave the lower back unsupported or create pressure points. This is why you’ve probably felt like you’re bouncing between “too firm” and “too soft.”
Given that your current mattress is only six months old AND feeling too firm (as opposed to too soft which is generally not an easy fix), trying a latex topper first makes sense before replacing the whole thing. A 3" soft Dunlop topper can be a good starting point for side sleepers who need more pressure relief, but (in my humble opinion) Talalay can sometimes be the better choice if you want a bit more “spring” and contouring feel.
Dunlop tends to be denser and a little firmer, while Talalay is bouncier and more pressure-relieving. If you’re worried about sinking too much, a 2" soft topper could also be an option.
If you go with a topper, adding a wool protector like you mentioned could be a smart move for temperature regulation. And if it still doesn’t work after that, then looking at a latex hybrid (like SleepEZ or one of the other Trusted Members) could be the next step. That way, you’ll also have tested the feel of latex before committing to a whole new build.
NikkiTMU