I have done this with 2 nics in each server with no issues. 3rd nic not needed if you configure correctly.

You can also use vNics, for instance if you have 2 servers with 2 nics, you can create ifcg-eth1:0 on the controller node and use eth1 for your management network and eth2 for your VM network.

Yes it is possible.

You will need 3 interfaces on the controller/network node and 2 interfaces on the compute node.

Those interfaces can be vlans. In that case, you could use just one physical interface per node. It is mode complicated to setup, however. This can be with virtual interfaces as well

Yes you can. I have done just that. Each node has two NICs: eth0, and eth1. Eth0 provides the interface to the physical LAN while eth1 serves as the private network. I have documented the process that I used (culled from many google searches and much trial and error - thank you to all that posted their experience and knowledge to the web). I have wiped and repeated this installation process several times so I know it works. I want to share my experiences but I'm not sure if this forum is the correct place to post this 500 line instruction.