Since you already have it, go ahead and swap it out. Try it for a week or two and see if you can tell a difference. What sort of frame have you got under the queen? If it's a metal one, I bet it will fit your double. I have a double, and they don't really make stuff just for doubles, you see them labeled queen/double all the time.
Transform = rearrange. I rearrange a lot. One of my rules for furniture is I need to be able to move it myself, because if I want to move it to a different room I want to be able to move it! I've rearranged my furniture here in the apt a couple of times. I like the living room better, I'm still not thrilled with the bedroom but it is better.
Can you put the dresser in the closet? I had mine in there until I found a sewing machine cabinet. Now it's in the closet and the dresser is back out. My bedroom might be a little bigger than yours.. I have the computer desk and shelves on one wall (pretty much eats it up), and the bed longwise against the wall in the opposite corner. The dresser is at the foot of the bed, and then the nightstand is in the corner on the other side... So wall, bed, dresser, nightstand, wall. There's no more than two inches between any of them. I use the nightstand to put my overnight bag on, so it works fine like that.