Trying to Edit Body Package, Ran into Multiple Hurdles; Please Help?

I’m trying to edit the Classic Male v2 LowerTorso and UpperTorso for a project that I’m working on, but I’ve stumbled across multiple problems that I can’t figure out how to fix on my own. I was trying to use a StarterCharacter to apply it, but that’s not working.

I’ll be referring to this GIF as I try to describe it the best I can:

Problem 1: The most obvious problem is the texture malfunction. All I did in Blender was slimmed the torsos a bit by grabbing their pre-existing vertices and dragging them back two grid blocks, I didn’t add or delete any vertices. When I imported torsos, their textures were completely wrong and I’m not sure what’s causing it or how to fix it.

Problem 2: The model on the right-hand side of the screen is what happens after I edit the meshes of the StarterCharacter and press Play. I’m not sure why it causes them to revert to the original mesh, but keep the messed up texturing. I can only achieve the proper meshes (left-hand side) if I edit the meshes after starting the Play test.

The model in the middle is what it looked like before I did any manipulation. I’m trying to fix the way clothing textures wrap around the torsos, but I have no idea where to start. I feel like if I can solve that problem, then I should probably be able to just edit the meshes using a script after the Play test has started.

I used Blender 2.8 to edit the meshes. I’m a complete novice at Blender and only know the basic hotkeys and functions.

Please help!

Edit:
I tried simply re-sizing the torsos, but that still doesn’t work. When I Play test it, the torsos fatten themselves back up. I can’t resize the torso after the Character is loaded, because it will die.