Yes you can screw directly through the formwork into the slab. That formwork shown there is either Bondek or Condeck. If you intend on fixing to this do not fix to walls as well as there is likely some differential movement that may lead to cracking of plasterboard down the track. Your local plasterboard and/or ceiling contractor will be aware of this. They typically screw timber battens or metal tophats and level the ceiling for the plasterboard to be fixed to.

It depends on the thickness of your mattress. I have a fairly standard height king mattress, on a ensemble base. I bought a standard AU king duvet and it shows a lot of mattress. Then bought a West Elm US king duvet and it's much larger. It covers the mattress, tucking in would be possible but your not able to tuck in a lot of fabric. I love the larger West Elm duvet, but they weren't selling well as the sizes were different from our standard, so they now only do smaller AU sizes. And the US West Elm site won't sell to AU... So I think if you want a generous duvet or quilt to tuck in. You may need to go custom made.

what a lovely room which needs to look the way that makes you happy but you may find that the shutters also get in the way when opened..i wonder how venetians fixed inside the window reveals and directly to the doors would suit? Sheers are gorgeous but i agree the curtain pole doesn't look right: the sheer curtain tops should cover the pole (depending on the track this may only need a different hook to hold the pleats up higher) and as you need something that can be pushed completely out of the way a different pole with proper drawstrings with the curtains tops covering the poles may be the answer: a chat with a specialist who does shutters as well curtains (Spotlight?) should help but i hope you keep the sheers

I love linen.com.au have similar as does Etsy. I searched French ticking doona.