posting values to the TMR0H reg when the timer is in 8 bit mode , how is that going to work ?
normally TMR0H would be cleared

Code:
TMR0H = $63               ' preset Timer 0 to a 10ms timer
   TMR0L = $C0
I cannot simulate any of your numbers in the mcc 4/8/16,64 MHz fosc produce different 8 bit reload values that match none of your figures
what is your clock source ?