Just out of curiosity, what will you be using the heater for?
1. Dripline is good
2. If you decide to use FF, GB is sufficient for veging. You can use Big Bloom if you choose during veg, too. Here's their chart for hydro
http://www.foxfarmfertilizer.com/hydrofeed.pdf
3. Water needs to be cool between 65-75F.
4. I'm honestly not sure about the ppm... Sorry.