Since you are having problems with manual configuration you can try a couple of more things. Enable option 43 on your dhcp server. Option 43 is a vsa that allows you to designate the address of the controller. The other way is to attach the AP to a switch port that exists on the vlan with the controller's mgt interface. This will allow for LWAPP discovery and remember the location of the WLC. It's commonly referred to as "Priming" the AP. The exact steps fpr each of these methods are listed on the Cisco website. Just do a search for option 43 or LWAPP discovery.
Another option is that providing you have other Access Points in the area, and the AP has been associated to a controller before, you can enable Over The Air Provisioning (OTAP) which will allow the AP to learn the WLC IP address over the air, from your other Access Points.
This is enabled from the 'Controller' tab on the WLC GUI.
I see your AP is getting an address on the same subnet as the WLC you are trying to assign the ap to. If your ap is on the same subnet as the management and ap-manager interface, then you have a configuration issue on the WLC. Make sure you set the time on the WLC via ntp or manually. What does the rest of the log show on the AP?