I believed that the Timer 2 interrupt service routine is too long and it is in same priority as Timer 0.You should try to set the timer 0 interrupt as high priority and all the other as low priority. Otherwise, you have to shorten all other interrupt service routines with same priority as Timer 0. One way of doing this is as soon as the critical operations are completed, push the starting address of the rest of the service routine into stack and generate a RETI.

Using software to re-load TH0/TL0 is difficult to generate accurate timing. The error in the timing is accumulative.