^There's a plastic rectangular piece inside the pelvis that houses both leg pegs. The plastic piece that I just mentioned fits inside the pelvis, but is not securely held in place and has a lot of room to wiggle around. That's why his legs are loose/wobbly at the hips.
To fix this, you'll have to:
1. Remove his trunks, which are glued in place to the plastic pelvis (easiest way to do this is cut down the seam along one side of the trunks, then peel them off the pelvis)
2. Open the pelvis by removing the 3 screws.
3. Find the plastic piece that I mentioned above and find a way to make it fit snug inside the pelvis. (I put a bunch of sculpy into the pelvis, pushed the plastic piece into the sculpy, removed the plastic piece, then boiled the pelvis to harden the sculpy). The plastic piece should then fit snug and have little to no wiggle room inside the pelvis, thus eliminating the loose leg problem.
4. Next, reassemble the legs/pelvis, and then superglue the trunks back into place. They're often glued too high on the pelvis, so regluing them in the proper position should take care of the gaps that you mentioned.
5. Superglue the seam that you cut on the trunks, and you should be finished.
Sorry for the long explanation, but hope it makes sense.