First off welcome to the board anonapersona. Oh and what an interesting name you have there too.
Now on to the questions:
1) There are a thousand different stem plants that you can have as a background. Actually you can have pretty much any stem plant as your background. Since you have a ten gallon you are just going to continuously have to trim it. My personal favorite background stem plant is Rotalica Indica.
2) What type of bulb is it? Is it in a swirl, is it pear shape, or is it straight???
DIY reflectors are pretty easy. All you woould have to do is get some tin foil and spread it above the light and find some way to fasten it. Try to get as little creases in the foil that you can.
3) I personally wouldn't recommend the powerhead in the ten however I would recommend that you get a small Aqua-clear mini hang on the back filter. They are excellent filters and won't cost you more than $15 at your LFS.
4) With the plants and the ac mini you can pretty easily keep a small school of fish, some ottos and a few shrimp if you wanted to. Say for example 2-3 ottos, 5-6 neon tetras and 2 amano shrimp. You should be fine with that as long as you keep up regular water changes.
I hope this helps but it sounds like you are well on your way to a sucessful tank already as you seemed to have done your research.