A CC reading of 0.4 is ok but if it goes higher than 0.5, you'll want to shock the pool.

When adding Borax, generally a couple of hours is enough for it to get mixed in well. Testing it again in the a.m. will be fine.

I do not know what trichlor tabs with zinc sulfate monohydrate are. I'll run it past Ben. But, definitely don't use the ones with copper.

Sounds like you are doing fine.