Welcome! First to the questions:
1. As many as you can stick in the tank!
3. Lots on this board have 21" or deeper.
4. Most don't use wands, especially during the day where it drives off CO2 that the plants crave.
5. Sand is okay for plants, but nothing special. You might want to consider replacing the blue rocks because they are likely a bit bit to be good for holding down plants, and blue really kinda clashes with plants, IMO
6. Your desired PH is really dependent upon your KH level. You'll learn all about the PH/KH/CO2 charts soon enough.
7. Yes, you will.
Now, please go read through www.rexgrigg.com
. A great FAQ on planted tanks. It will address all of the above and more. It's actually worth reading a couple of times.
As to cost, to get a pretty high tech planted tank, I recommend you figure around $20 per gallon. Certainly no reef like costs, but not real cheap either. Assuming you have stuff around already, you can probably reduce these costs somewhat, and if you want to stay with a lower tech approach, you could cut is a bit more. But, for planning purposes, it gives you something to think about. Oh, and that's about what I spent in the first 12 months to get my tank up and fully running. Since then, I likely spend less than $20-$30 per month (and that's with electricity).
Planted tanks aren't necessarily easy. But, if you're keeping a reef tank, you can certainly figure it out.