don’t know how many times i tell people watch my videos , they show the correct work flow and set up for getting vehicles into UE4 from blender
the only thing to add is un tick leaf bones
on the physics side again watch the videos and double check location and alignment of the bones, take what an hour or 2 to watch that will save you hours trying fix
edit just had a quick look at the pics, so pal but untill you fix the alignment of the bones the physics will never work