I'm afraid I don't follow you on that last one....not setting any port?
I'd move the LCD to other pins in order to free up PortB.0 for your "polled interrupt".
PortB.4-7 are, like I said, interrupt on change - they will set the interrupt flag (INTCON.0) on both the rising AND falling edge and you need to read or write the port to end the mismatch, then clear the flag. They are trickier to use the INT0.