I just tried readable and it seemed to work. Then I rebooted and St-Guide crashed when I opened a file by double-clicking. One improvement was that it did report that it was ST-guide that was being killed. I tried global and that did the same. Sometimes it crashed Thing as well as St-Guide.
"Readable" is good enough, there is no reason to relax the protection further to "Global" (readable at least protects the ST Guide binary from being accidentelly overwritten in memory, global does not).
When it is not Thing that gets killed, that means, that the problems you're having now with ST Guide are unrelated to protection status (as Helmut wrote).
Pozdrawiam KMK