Hi,
2/
TH2 = (65535-1000)>>8; ?????
TL2= (65535-1000);

this is a more generic approach and using the compiler to do some calculation for us. The 1000 is the number of ticks we want to load but the timer is an up counter (normally) and interrupts when it overflows (65535). This explains the 65535 - 1000.

Ooops, general failure has been found!

Not 65535. A timer overflows at 65536!!! So (65535 - 1000) gives us not 1000 but 1001 ticks. The simplest check: how much ticks have you expected with reload value (65535-0)? Zero? No. The one is right answer.

Regards,
Oleg