Polling the timer won't help, since it's the time it takes to execute the SERIN2 statement that causes the delay in responding to and reloading the timer. It can't do anything else until that statement is finished, and with a WAIT() in there, who knows how long it will take.

And INTCON.7 is the GIE bit (Global Interrupt Enable).
Setting it to 0 disables ALL interrupts, but does not affect the timer other than delaying the Interrupt Service Routine (ISR), which needs to reload the time to keep it accurate.

Depending on what your 4hz interrupt is doing, ... you may not need to worry about it interrupting the SERIN2. If the ISR is fast enough, it won't cause a problem.