@cyclone3d:
I also need to know if it is possible to:
1. Set IP according to MAC address
In pfSense DHCP can assign a fixed IP address determined by the MAC address of the DHCP client.
@cyclone3d:
2. (This one is kinda strange and hard to understand, but I will take a stab at it) - If a user has a specified IP by MAC address, and the user changes their IP, disable(block) that user.
If a user is smart enough to change the IP address they are probably smart enough to change the MAC address. If you are worried about such users it would be better to put them on a separate interface (or interfaces) and use firewall rules to restrict access.