I think it is pretty clear now that this is not a font problem.
Something appears to capture the keyboard input option-8 before the program expecting text input gets it.
It is surely a software issue, and not a font issue. We can at least set that aside.
I am not sure if this was asked and answered already (sorry if it was), but if not then it is useful to do another test: make a new user, login as that user, and try using option-8. Does it produce a bullet character or not?
The answer will determine whether this is affecting only your account or is a system wide problem.