Please can any body suggest which Netgear Controller can I use with my WAC 730 to be able to do VLAN segmentation.
You don't need a wireless controller to achieve this. Much more a VLAN capable (ideally PoE) switch, and a router able to deal with multiple subnetwork LAN(s) either by VLAN support, or untagged LAN[1,2,...] ports. Netgear has introduced Insight a while ago, and announced a Insight managed router (BR500) these days. Of course it depends on the scope, the bandwidth you need to pass between the subnets, ...
Sure. Check the fine documentation ref. VLAN and WiFi Security Profiles p.38 ff. with the VLAN config.
Again: You need a router able to handle DHCP (this might be possible on a controller by VLAN) and then the routing to reach other subnets and the Internet.
The WAC720/730 management VLAN can be configured, too. On that VLAN, you can either use DHCP, DHCP with a MAC reservation, or a static IP config - at your preference.