A lot went sideways here. Fixing THIS mesh/ UV isn't worth the effort. Blender unwrap won't set a UV similar to TS3's set up. I believe it was a pair of non-TS3 boots that we resplit and unwrapped. This is new mesh time. IF it had been only a few vertices, you could rip them and manually put them where they belong... but this many is too much work.
If you're making this into a top, you cannot have any UV in the bottom right of the UV map, as that is reserved for bottom parts by EA. Also, if your plan is to make this an open bottom, no top UV can cover the bottom legs area. But, I see you have a bottom close off.
I guess you're trying to work with and export as geom? If so, you MUST split seams as instructed by Smug Tomato! Also, you must split sharps using the same method (2.9x and up). It's always easier and safer to export as wavefront object, and convert in MTK, as MTK does all the splitting for you. Then use MTK for bones and seam fix. The only possible mess up is if two vertices that are not part of a seam are touching, and got merged. MTK often misses this, but that's only one vertices to fix.
I recommend for this project, do not move the top garment UV. Use the knife tool to trim excess from around the female neck, then adjust both the mesh, and UV to fit. You may need to adjust the back of the neck, but the texture mismatch should not be noticable.
Mirror the whole left arm UV, including skin, and overlap the right arm to give you enough map space. The issues are that sleeve textures will be the same, and arm tattoos don't look good.
Use resize to shrink the belt/ trim and bottom to .8 on x and y. You can then use percentage in GIMP to shrink those parts of the texture by the same amount. Move the belt/ trim UV to where the arm was. Stack the bottom UV, and move to space reserved for top parts.
It might help to import a bottom mesh, so you see the UV and don't overlap it.
Get the basic mesh first, with working UV, textures and bones. Af tunic looks like a good donor for bones and morphs.
After you have a working package, you can go back and adjust the mesh to a more female appearance. Separate the hands and neck, so they are not changed, especially the neck seam. Use af swimsuit plunge mesh as a guide to narrow the waist, back curve, hips, butt and breasts. The UV won't change at all. Then, rejoin the neck and hands.
Shiny, happy people make me puke!