How to measure the radius of a fillet on a non 90deg angle
I use low tech things for that kind of stuff. Bottle caps, jar lids, rolls of tape, 5 gallon buckets, whatever may fit the curve I am trying to measure. Once I find one that fits the curve, I measure the diameter and divide for the radius.
There is a formula for finding diameter if you can set a straightedge or at least create a straight line between 2 points of an arc.

I will need to find it and add it later. It is very simple, and I used to use it a lot...