1.) There are really no benefits to CC (crushed coral) that I can see. CC trap detritus cause major problems down the road with nitrates. Sand on the other hand, doesn't do this. Sand allows certain fish to burrow and slide along the bottom without causing injury. Make sure your grain size of sand, should you choose to use it as a substrate, is not too small (smaller than a grain of sugar), or you will have issues with it being tossed around by your filter/powerhead. CC only offers the calcium buffer at a lower pH that you will not see in SW
(under 7.5 IIRC).
2.) I would recommend two powerheads, but you do have your filter, so you should be able to get by with just one. Try to aim for a 20x-30x turnover rate per hour (GPH
ratings). With powerheads, a good starting point is aiming one at the other towards the upper, front-center glass. This provides excellent oxygen exchange as well as a nice, chaotic flow just like you would find near a reef.
3.) On a tank that small, your simple 10%-20% weekly water changes will accomplish the same thing that a skimmer would. To put it simply, just keep up the water changes and spend the money elsewhere.
4.) Put you base rock in first right on top of the bottom glass, then pile the live rock on top of the base, or either way, it really doesn't matter, I just liked having the nicer live stuff on top of the base. Then, add your substrate to cover the rest of the visible bottom glass. Putting the rock directly on top of the glass helps avoid slippage should something decide to burrow under the rock.
5.) Don't supplement anything. Everything you need buffered, your salt mix will do for you, and anything that needs replenished will be done so by your water change. Later on, you may find the need to supplement calcium. Rule of thumb is to not supplement anything you can't test for.
wouldn't be a bad choice in a 10g as they are rather shallow tanks. I wouldn't worry about the heat. I kept my tank around 81 degrees intentionally. A 70w halide fixture isn't bad either, 150w, depending on the placement will bake your livestock.
is a horridly out-dated rule. Factors such as PAR, intensity, and depth penetration are far more important. A good PC
fixture should maintain those corals you listed without a problem, even the majority of LPS
corals would do fine. Below is a good link on lighting that will clear some things up.
Aquarium Lighting; Kelvin, Nanometers, PAR, Bulb, Watt, MH, LED, Light Basics.
8.) That would be a fine amount of water to change weekly. I don't recommend getting two gobies for that small of a tank, maybe a yellow watchman goby or a clown goby and an ocellaris clownfish.
If you have any questions, please ask. By the way, welcome back, I haven't seen you on in a while.