A skimmer doesn't remove detris, it removes dissolved organics in the water (invisible scum, put simply). Stick to your existing plan for snails/crabs.
I wouldn't go any thinner than .1"...you need this to be rigid, not flexible...if it flexes you'll break the seals and have a mess.
photos you linked to appear to show a standard maxi-jet powerhead. No parts are 'removed'...you simply don't attach any of the parts that come with it (intake extension, outflow director, etc).
My guess is that it also uses the 'venturi adapter' to get air whipped in. You can get those for like $5 from premiumaquatics.com