distributor hold-down prevents timing adjustment?

HEAT UP a cheap wrench and bend it. You can do this with (in a pinch) vise grips or pliers and a propane torch

In my (old age) I've got wrenches that were bent, re-bent, cut and welded to a different angle, and "grinded on" to reduce the cheek size. One 1/2 inch I used to have was done specifically for some tight clearance carb mounting nuts, years ago