Ok well Imo the core issue isn't really the brush up part on FH, you brush up plenty (at least at contact), leave balls short if anything... its your takeback. You take a very short low backswing with almost no loop to accelerate the racket. Most atp have racket head high at unit turn start accelerating rh with a loop. You kind of just drop the racket down behind you and lift the ball forward and up with your arm, not a lot of torso coil, lag or explosiveness. Tough to get easy power or have much depth. I'd look at your prep and takeback form. atp guys today are more compact than say, Lendl, who had that big signature loop, but you need a high unit turn and loop to get you into patdog and then into the slot. Do that whole shoulder tucked under chin thing.
i modeled my fh more after ferrer... and i go out of my way to keep my hands low on the take back (less moving parts for slightly less power)
i'm not sure what you mean by "not a lot of torso coil, lag or explosiveness"... because i'm hitting on the run, or in general? in general i think i am doing this.