Beneficial Bacteria or BB is killed when everything dries out so no, unfortunately there'd be no BB left and so you have to cycle all over again.
1. I say do planted, you know me lol
2. Here's a list of low-medium light plants: Java Fern, Java Moss, Anubias, Anacharis, Cabomda, Common Cryptocoryne's, Water Sprite, Water Wisteria, Hornwort, Moneywort, Frog-bit, and that's all I can think of right now.
3. For silk, I bought mine cheap from drsfosterandsmith.com right now since they have a summer sale but most place you can get them from are Amazon, Ebay, ThatFishPlace.com are my favorites.
4. Hides, they like things to hide in so anything that has caves they can swim through.
5. Glowlight Tetras, Microrasboras, Harlequin Rasboras, Cherry barbs, Neon Tetras, Celestial Pearl Danios if you want to order them, Endler's Livebearers, Guppies.
6. Add extra Sponge foam to the out flow and you can also stuff the intake with foam as well or wrap foam around the outside.
7. Don't use an air pump, Betta's need to breathe and don't like water being moved around that much. You know how Ragnarok get's really angry with the filter flow? Well he won't like an air pump either.
8. 76-82 is the best range, 72 is a bit on the lower side. It won't kill them though, it will just slow their metabolism down and they'll become more lethargic but 78-80 is the best to aim for.
9. Anything that's adjustable! My personal favorite is they Hydor Theo, on sale right now at drsfosterandsmith.com! http://www.drsfostersmith.com/produc...8&pcatid=11368
50 Watt for a 10 gallon, 50-150 Watt for a 20.
10. Anything honestly, I've got sand as well as gravel. You can use anything basically, even bare bottoms. Easy to clean, IMHO, gravel since you don't suck it up as much as sand. Good for plants, sand will keep most things rooted easier but they can root just fine in gravel as well. I use black gravel to bring out the Betta's colors (unless they're black or darker) and in my 10 and Rembrandt's 3, I'm using gravel and the plants stay just fine