There is a fun and functional way to test out what your best starting point may be for handlebar width and sweep. Grab some dumbbells that have flattened sides and use these as your "handles" while you try some push-ups in different positions. Rotate the dumbells, move them wider and narrower. Try to find the position that is most comfortable and also feels powerful. Pay as much attention to how your wrist feels and looks at the top of the push-up as you do lower into the push-up, although it's the middle part that is most important as this is where we ride. When you've found your happy place, leave the dumbbells in position, you can measure them for width and take note of backsweep.
Mountain bike handlebars don't come with consistent sizing rules and this is the best way I've been able to think of to test it before you buy it. One rule of thumb is 10 to 15 cm wider than your shoulder width.
It sounds like you've already found the right width for you so I would guess that you might want a handlebar that is more backswept than your current set up. It would be great if you could put the handlebar on, and just get your hands on it to see if it's in the ballpark, without putting shifters etc on. Then maybe you can try a few different ones.
You might also want to look into some different grips.
These Ergon grips saved my bacon in Portugal last year just because I had a lot of different hand positions to go to. I think these are more appropriate for endurance riding but something similar may help you.
Finally, make sure there isn't a subtle change you can make to the position of your shifters and brake levers to take some creasing out of the wrist