I wonder why they did this? Particularly the floor. They have created a really nice trip hazard. Was the sub floor not level? I think you have limited options to fix this. You don't want to increase your entire floor level to match it. You will likely need to remove and re-install the stackers. I guess it will depend on the architectural detail on your plans, as to who pays for this. I think paint will resolve problem 1.

Proportional consistency - keeping the 1:2 rule in place everywhere will jar less than having the same architrave but varying the skirting. If you’re already considering 90 and 140 skirting, why not go for 40 and 70 architraves? The effect will be more harmonious and it shouldn’t impact the price too much ... plus, it’s your house - if you like the 1:2 rule then use it :-) (PS: if it does impact the price too much, just pick one size of each and save more cash)

There are indeed building code safety requirements that govern the design of balustrades, including the gaps around panels. Sometimes compliant gaps at the maximum opening look a bit off. I find that smaller gaps, 20 - 50 mm often look more pleasing. You say your patio is not covered. In that case there is little potential for any balustrade to trap heat. An uncovered north facing tiled patio will be a heat sink, and a glass (or substantially open) balustrade will allow more sunlight onto the tiles which will increase heat gain. A solid balustrade may reduce that heat gain due to it's shading potential, but I am guessing you want glass for the view, so if heat is a problem, consider adding a roof covering to shade the patio.

I was going to suggest that the shower and hanging for togs and towels be placed in the red zone using the pool house plumbing. It looks great where you have it but it should have somewhere for the togs and towels as kids will use them several times a day in hot weather. If the Pool House was a POOL house and open to the pool would that mean you could just fence it and the pool together, but I guess by being multi function that changes the rules