not sure if it's the part of the underbody texturing you're about to do, but you can see through the inside of the fenders, visible in your first and fourth screenshots.
I've noticed 2 issues: custom skins don't work in LOD2 and LOD3 and you might want to get rid of the remnants of the badge in the front mesh or at least change the shape.
You can invert and assign the axes in the options, controls>axes/ff
as for the steering issues, i'm not really sure if it'll help, but try increasing the axis range from the default 1000 and play with the wheel turn compensation setting