I do use clips - sorry I forgot that step. I couldn't find a metal skimmer cover last year although I have heard about it - it seems valid and you don't have to replace the skimmer face to install it. As I understand (haven't done it) you remove every other screw from the skimmer face plate and put them through the metal cover.

I see no reason not to keep the water level and use a metal plate (with o-ring or gasket) and a sealed plug in the return. It's not how I did it but I would.

CarlD's pool is much stronger than a traditional AG and can use a mesh safety cover. On a traditional AG, a large weight (my bigness) on a cover supported only by the pool walls would probably cause the walls to fail.

All I used last year was bleach - I did close after the water was 60-55 F and opened early in April. Polyquat should give you an earlier close and later open. but... if you do go green, you know what to do