That shouldn't have killed it but obviously you have a dead controller. Did you change the current limit settings at all?

I would recommend running the ragebridge on 6s. I have had great success with PP3D and crossfire running them at those voltages on T64s.

As far as repair goes, I'm aware that there is someone on the continent (name escapes me) that can repair controllers or you could see if Rory from nuts is able but as to whether it's worth it cost wise I'm not sure because I've no experience of it.