Currently, HMD just slaves to wherever my mouse points. Is there a way to make it slave to something else without moving my view?
No? You can manually slew the radar in regular modes though. Or just use vertical ACM.
I can’t move the ACM box on F-4J. Is it just permanently locked to the bore sight?
Yeah it is, but vertical ACM modes are about as close to getting HMD without it being binded to your mouse. Dunno if the F-4J has a vertical ACM mode though.