How do I edit CustomTrackShape?

Question

I am designing a custom track shape for a project that looks like this:

and I already finished most of the code, I ended up with this result:

aside from the rounded sides (those I'll fix), I need to achieve:

1. Move the label under
2. Change the label dimensions if possible
3. Customize the trackheight to make it smaller on one end and larger on the other.