1. DT interrupts are just ordinary interrupts (except that Darrel has made them easy to use). So normally, I would say YES. But in searching through the PBPPIC14 LIB, I see that WRITE_INT is only used for WRITECODE. It is not used for READCODE or ERASECODE.

Flash READS and ERASES probably aren't so time critical, but It never hurts to turn off interrupts when you don't need them, especially if your ISRs take a long time to run.

2. See above.

3. WRITE_INT is not a toggle. It turns off global int at the beginning of the WRITE and turns them on again immediately after the write.

4. I believe you are correct. I have performed this operation before - but that was several years ago.