If you want it to interrupt when RB0 goes high, comment out the OPTION_REG line and use external resistor from RB0 to ground.

With the OPTION_REG set as you have it "pull-up""set" the pin will need to go LOW to trigger the interrupt. No external resistor.
From data sheet.
External interrupt on the RB0/INT pin is edge triggered,
either rising, if bit INTEDG (OPTION_REG<6>) is set,
or falling, if the INTEDG bit is clear.
I counted to 255 then of course it rolls back to 0 and starts over.
I guess I should also disclose that I am using the "EasyPic4 Development Board". I wonder if that is my problem.
Not sure, never used the "EasyPic".

I am using Ubuntu (linux) for an OS, running MPLAB with PBP as the language set via Wine hooked to a PICSTART PLUS rigged as an ICSP.