Here is a list of break points to put in ~/.gdbinit that are really helpful in debugging memory problems:
fb -[NSException raise]
fb -[NSAssertionHandler han
The title of this indicates that you are asking how to set these in ~/.gdbinit but the first line of your detailed question indicates that you have the above in ~/.gdbinit?
What, exactly, is the problem, then?
I use something pretty similar and it works fine, but since much of this is fairly intrusive behavioral changes, I put it in a separate file (~/.gdbmem) and then source it as needed.
My ~/.gdbinit is limited almost entirely to macro definitions that don't otherwise change the debugging session. Thus, the default behavior is minimal impact on debugging and I can source one of 2 additional files full of gdb config goop to automatically apply some relatively intrusive additional configuration to the environment.