You will not get good uv_0 through uv transfer because your pants have very different topology, the seams dont match, folds overlap.
It'd be a better idea to just adjust the uvs from MD to match the maxis ones;
- join both sides of the pants together, do the same with the reference;
- move and resize the uvs to look like in the first pic;
- close those gaps with W - Align X;
- move the uvs in the belt area to be more-or-less even;
- select the borders of uv islands and pin them;
- press Q, open the side menu, choose Relax, increase the radius, press in the stretched area;
- select the reference, shift-select yours, View - draw other objects to see the uvs of the reference;
- select all uvs of the pants, press S Y .5 to shrink them vertically, resize them to fit;
- if you want, you can open the gap between the legs