1. what clay said
2. there's crete/grout and the binder/bonder method to add to clays answer...
3. water proof... depends on the definition you're using... it's a sponge once it's cured... but inert.... so it doesn't hold water back but is safe... gaps and cracks and pond and stone are usually used... big gap filler swells huge and leaves huge bubbles... windows and doors has an additive that makes it flexible... and doesn't always completely cure... can leach toxins sometimes.
4. what clay said
5. if you like the look of swampy waters you don't have to leach the tannins out. you're looking for something not soft (can't press your thumb into it), not scented and without sap. soaking and baking can kill the critters also. the flash point for many woods is just over 350* F so keep your oven ~300* or less and keep an eye on it once it starts to dry. there are other tricks you can use for preparing wood if necessary, but that's the basics and the common ways.
clean it whenever you get a chance. wipe down the glass, pick up any noticeable poo, turn the soil wherever you see mold/muck/issues (if you can). do not change the soil. vivs are naturalized environments. the forces/cycle of nature is mimicked on a small scale... microbes grow, mold grows, moss grows, plants grow and take hold... animals are added. changing the soil starts the cycle all over and is cause for mold re-occurrence.
you're looking for a pump with +/- 100gph @ 2' head height most likely. internal filters/pond pumps/repti-flow filters/canisters/waterfall pumps (cheap and usually sturdy)...
i'd definitely look for something adjustable or put a ball valve on the output to adjust it. pumps tend to run slower over time so being able to choke it back at first and adjust over time is a major plus and helps keep your desired flow.
definitely take the time to check out all the stickies. you'll get lots of ideas and answer a lot of your questions. also check this thread out...
how it's done... favorite links thread
welcome to the site.