Herbie Overflow Question

[YEGReef]

Purchased a used 225 Gallon from a seller and they were using the Herbie Overflow method, which I want to continue using, just had a few questions.
Disclosure: I am using it for freshwater but Saltwater hobbyists I find have more experience with larger tanks and sumps.

The Water enters section 1 and eventually makes its way to section 4, where the pump will be. Leaving section 5 and 6 empty and sealed off from the rest of the setup.

1) What section should I place the emergency drain pipe?
Section 6 actually opens up to section 2 on the top, was it may be used as an emergency section in case the sump ever overflowed so should I keep it empty? Section 5 eventually overflows into section 1, maybe that's a good place for the emergency?

2) Do you think I have the main drain pipe at a good height in the overflow box, but the emergency should be a bit higher?

3) My PVC cuts were not 100% straight, but still a tight snug into the couplings, would that be fine once I glue it all together?

4) How do you compensate for evaporation, don't you want the water level for the emergency drain to just be entering the pipe just a little and don't you want the sump level to stay at a particle line as well. Are you refilling water every other day or so?

I have attached photos, thank you and sorry for the long post!

https://i.imgur.com/OdmUkNP.jpg
https://i.imgur.com/WVwetpq.jpg
https://i.imgur.com/w9GPAWE.jpg