Could probably use another 2 degrees initial but certainly needs about 4 degrees more total and that should be all in by 2000 or 2500 at the latest.

Dual exhaust is over rated an equal cross section single flows more and retains heat better. Make sure you have good merge points and you should be fine with a single 3 or 3.5 inch pipe.

Go back to the 750 and lean out the jets till it starts stuttering and go back up one jet size.

Open your plug gap to about .045 with that ign it should produce a hotter spark and light the crappy low speed mix better.

Thats about all you can do without tearing into it.

I am convinced in the cam making a huge difference. Get a custom made cam, the few extra $ will be worth it but even a small summit cam advanced a couple degrees will be better than what you got, I just hate tearing into my junk and sort of fixing the issue. It will reduce overlap, close the intake earlier for more cylinder pressure and open the exhaust later for a little extra push on the crank before releasing cylinder pressure. It will result in more power everywhere you need it and you may no longer beconcerned with the RPM drop. A big RPM drop ain't as bad when there is TQ down low to take over after the shift.