I’d split the UV’s up a lot more, at least temporarily for this stage.
Clothing is just a bunch of flat pieces of fabric, stitched together. It’s pretty much the real life equivalent of UVs when you think about it.
Try to look at the pants, break down where all the individual pieces would be, and place the UV seams accordingly (match them to the actual fabric seams). On most pants you should be looking at at least four pieces of fabric, each leg having it’s own front and back. The result should be pretty easy to apply the pattern to, and give a more accurate result then having both legs share the same island (note how the pattern on the fabric shouldn’t quite match up along its natural seams, such as along the middle where the zipper would be).