Mesh detaches from sim

Are you planning on making the top part see-through? If not, delete all area of arms covered by clothing and put uvs there. Also, you should have split those big uv islands in the arm area to have easier time fitting them in the available uv space. The smaller the uv islands, the worse the texture quality. For that reason you also should not scale them individually, will lead to differences in texture.
Also, it's best to not put anything in that bottom right corner because everyone puts everything in there, so if you do not want someone telling you to "fix your cc" because some mf put uvs for eyelashes there, is2g...

Also, make clothing in quads and do not lower Particle distance to this extent, the mesh will morph and animate in a cramped paper type of way no mater what you do.

What you should do:
- go back to MD, select all patterns, right-click on them and choose Quadrangulate;
- raise Particle Distance to something like 15 or 20;
- split the front and the back of that top piece either in half or in 3 parts;
- export as weld;
- clone lingerie set, export the blend, open, import the clothing, do not hide the lingerie set;
- create and transfer a uv_1 map;
- transfer weights;
- vertex paint with 00ff00;
- delete all parts of the body covered by clothing;
- edit the uv_0 and join the garment with the body, assign cut number;
- import in s4s, test in-game, make maps, do lods.