I am using Ubiquiti Airmax PowerBeam units for a similar situation. What I did was plug the main unit into my network and at the second location I have a switch with two units. One is synced with the main unit and the other faces the third location where I have another switch and a forth unit. I couldn't get PtMP so I went this route and it works great! They are weather proof so they can be mounted outside. I suggest the Ubiquiti NanoStation Loco M5 and 2 TP-Link 5 port switches.

NanoStation - you will need 4

Switch - you will need 2