Distilled water and Preperation H? When did you last compete, in the 70s?
Distilled water is a good way to go completely flat and cramp. You need electrolytes, even when cutting sodium out, you still need some sodium in your body.
Preperation-H cream might pull some sub-q water but only if it has the active ingredient Bio-Dyne in it. As far as I know this is only available in Canada (not sold in US with Bio-Dyne), not sure about Europe or other countries. Before people jump on me how well it worked for them in the past, you can just wrap your stomach in saran wrap without any cream and have the same effect. So unless you actually had Preperation-H with Bio-Dyne in it, you could have just lathered yourself with butter and had the same effect. You will sweat out a bit of water. Very temporary effect. Will probably last for as long as you don't drink anymore water lol. Doing it last minute, a very good way to screw up your tan.
Lastly do not mess with potassium, especially if you are taking a potassium sparing diuretic. This is how competitors endup hyperkalemic and in the hospital rather than on stage.
Like many people already advised you. Stick to the plan. Don't stress. You look good. You're thinking that doing some last minute "tricks" will make 10% better, but it's 90% chance going to make you look worse.
You are stressing more than guys stepping on the Olympia stage. You look fantastic. There are no last minute magic tricks. What you look like now, you will look like on stage. Accept that fact, enjoy and showcase what you worked so hard to build with a proud smile on stage.