Hi, I've been working on a late 1970's Epiphone Crestwood and need to make adjustments to the neck angle. Currently the neck leans too far forward and make the high notes hard to play(as well as messing up intonation) as the strings are too high. The lower notes are too low and cause severe fret buzz if I try lowering the action. The bolt panel says right on it "Steel Adjustable Neck". However I'm having difficulty adjusting it(keep in mind I'm a noobie). I tried putting a shim at the bass of the neck under the neck pickup but it didn't do much. What would be the best way to lean the neck back?

Here's a pick of the guitar if it helps(not my actual guitar but the same exact model)