[grahamburger]

I'm not currently building a WISP, I'm building an auxiliary business for WISPs (Email in my profile if you're curious what it is - not really trying to promote here just yet) but since you asked I'll answer from past experience:

1) I've used Cambium and Ubiquiti and several others. Ubiquiti is hard to avoid because it's so damn cheap and it does work reasonably well, although Cambium is noticeably more robust. The latest stuff coming out is fixed 4G LTE, several companies pushing that gear in to the WISP space and I suspect that's where things will start to take off.

2) 30-50 for Cambium and Ubiquiti APs. Fewer if possible. On a large network the APs tend to be the bottle neck.

3) Fiber to primary POPs and then high capacity licensed wireless backhauls 2 to maybe 3 towers deep in the network. Depending on the local weather it's not unrealistic to get a licensed link that can support 800mbps to maybe 1.2 gbps over 3 to maybe 5 miles.