For 802.1X EAP support, a back end radius server for authentication is required. After we check the “Enable IEEE 802.1X” support at interfaces page, where shall we enter the ip address of the back end server? Does pfSense use the same radius server for “Captive portal” and 802.1X?
8021.x is not fully supported in the current version. It will be in 1.1. If you want the support you need to hardcode the values in the hostapd.conf.
The hostapd.conf is generated int the wireless section in /etc/inc/interfaces.inc. If you want the config to be generated correctly for 802.1x on reboot or other changes you will need to hardcode your settings in /etc/inc/interfaces.inc. And no, the captive portal radius config will not work with EAP afaik.