We had a cal king and it was a PIA to find bedding. I would go with the King, after your eye gets used to it, you won't miss those 4 inches at all. We dropped sizes from a Cal King to a Queen now THAT was an adjustment, but I love being able to stay warmer at night and the bonus is bedding is less expensive. Rule of thumb, function over form. If it will work better for you, go with the king.

I like all of your upholstered choices shown. I think they will work nicely with your desk and do have an elegant feel, although I've always been partial to iron beds. If you're still looking at iron beds I can recommend Charles P Rogers. Great customer service and my daybed is high quality with a beautiful hand painted finish, much like the antique iron bed I have in DD"s room. I had a Wesley Allen and have seen RH beds - all nice but they don't seem to be as heavy and sturdy as my Charles P Rogers bed. Another iron bed company I'm interested in is Brass Beds of Virginia but I haven't seen those in person.

There is always room top/bottom to accommodate blankets and such. That should hold true for just about any head board/ rails/footboard style bed. It does sound like you have more than average. A standard kind is wider and shorter than a CA king so it isnt to accommodate the size difference from one king to another as many beds have the option of moving the rails from king to CA king. a CA king is the longest mattress you can buy that is considered a standard size. Since you have had the bed so long I doubt there is anything you can do to remedy that situation.

My sister bought a memory foam mattress and she and her husband had issues with heat retention. I gave them a 3" natural latex foam topper and the problem was solved. Memory foam works through a chemical reaction that loosens the bonds with heat, making it softer where it is warm and more firm where it is not warm. It is also quite dense, reducing air flow. What happens is that you sink into the mattress where you are laying and the mattress becomes softer where you are laying, so you get trapped in the hole. This will not happen with natural latex. It does not change density when exposed to body heat. Factors impacting mattresses sleeping hot are body weight and mattress firmness. The heavier you are and the softer the mattress the more likely you are going to sink into the layers and create a trap for body heat.