Chrome keyboard shortcuts while playing local videos?

Solution 1:

There indeed are no other keyboard bindings than the Space you discovered, and there seems no user exposed way to add different bindings without resorting to browser extensions.

Obviously, there are many video players dedicated to play local content that do have a range of shortcut keys, that eventually can be customized. If you are concerned about security while playing a local file, then you can install such video player as a snap package: applications installed as a snap are also sandboxed. Alternatively, there is a tool firejail that allows running applications in a confined environment ("sandbox").