I'm doing the same. I've settled on the Reynolds (it is bleached, but it seems to be the best quality and easiest to work with). I also have to double layer with every type of parchment I've tried, or even at 1 ton of pressure with up to 4g I get bleed through (puck of maybe 1.5" diameter so we are looking at a PSI of >1,000 at 1 ton ...)I am using any baking paper (not wax paper) I can get at the supermarket, mainly unbleached. The only issue I have is that a single layer does sometimes bleed through onto my plates. I think this is mainly due the the extra pressure I can excerpt with my big press. I tried some SlickSheet yesterday (still had some laying around) and didn't like it because I found it difficult to get the rosin off. When I cooled it enough to get it off cleanly it turned to shatter and jumped all over the place. I think I will go for a double layer of baking paper for my next press.
I current store in silicon containers inside another container in the fridge. Never noticed any issues even after months of storage.
I'd really like to get some 35lb parchment from somewhere, but can't seem to find it anywhere in Canada at a reasonable price shipped. (this is what the slick paper is I believe ... 35lb parchment ... could be 55lb as well I guess, but I doubt it ... likely just generic 35lb parchment cut to sheet size and than packaged and branded ...)
I've seen some "Bakers Choice" 27lb platinum silicone and 35lb silicone parchment online (16.375" x 24.375" x 1000 sheets), but haven't found a source/price for it in Canada where they will ship it to me for a reasonable price.