How can I customize the Touch Bar interfaces for my tremor?
Many of us have difficulties with aspects of UI design, both in hardware and software. Look past the frustration and think around the problem. 

A simple fix for me was to attach an external keyboard, wired at first, but then wireless using a Matias 101-key keyboard with the number pad on the right, a design I've been using since the DEC VT220 terminal keyboard came out a few decades ago. I also use Apple's wireless trackpad, which is larger, and sits where it should be - next to the keyboard.

I see Matias now has a backlit model! How cool!

Be well. Take a deep breath and center yourself.