How to make a Chromebook less demanding of fine motor control?

I am advising a Chromebook user who has difficulty with fine motor control. The user has a Chromebook with a stock Chrome OS install. This system continually demands fine motor control, and when it doesn't get it, it throws up obstacle after obstacle. For example, menus are a small part of the screen, and disappear if the pointer moves even a little off them. Accidental clicks activate an unwanted feature. Accidental control-key presses bring up unwanted power features, including in one case a web developer's toolbox in a GMail window.

Google's page   has a video about text entry with dictation, and mentions of keyboard assists like "sticky keys" (to make control key combinations easier) without specific documentation on how to use it, but doesn't talk about disabling unwanted click targets or control key shortcuts in a way that would help this user.

What actions can I take to simplify this Chromebook?