Friend had same problem.  Bought a stick car and converted to foot brake.  Couldn't hold the car, so had to switch pads.

Wow..didn't know those Performers fell off so early?

Better then what my friend did.  His was on the tilt control lever(rh side of column foxbody), let go and then have to reach over for shifter to grab second gear.  Yikes.  He did it for many, many years.  I drove it once and was like "nope, not me".

Well, that is likely your lean out condition, lack of pump shot when going WOT.  You need a pump cam that is longer on taper instead of short.  Don't know what they offer for 50cc pumps(I assume that is what is on the carb).  Holleys usually have two spots to mount the cam.  It rotates it, so moving it later would add to the distance it sprays on throttle position. 

Many guys use a two step for launching.  I tried it years ago.  Back then many of the nostalgia events classified a 2 step as "electronics" and you couldn't use them.  Thus I removed it and never used it in the last 20 yrs(this is my 22nd season racing the wagon).  My two 600 Holley's are vacuum secondaries and I have 50cc pumps on them so it gets plenty of fuel.  My secondaries don't open until I hit high gear(bout 1/8 mile).  By testing(unhooking), the 1/8 miles times are not affected.

One friend put his line lok and two step on a button and manually releases it at launch.  Others mount switches on the clutch pedal to do it automatically.  Though you need to adjust them very carefully as you need the clutch to be grabbing at the same moment the 2 step releases.  If not, it will either bog or the RPM will rapidly climb way higher then you had it set for.

What carb are you running?

I picked up 75 hp!  No other changes(really, nothing).  Granted you aren't going to see that kind of improvement....but you will notice a much stronger pull down low.

If you go with faster gears, I would try the Performer.  The gears will really need torque to get you moving.

Yes, taking the gap from slappers makes it ride rough.  Been there with my '69 F100.  I want to get ladder bars back under it someday, but the slappers at least get me by.  Tightening the gap takes some of the stored energy from the springs wrap up from hitting the tire.

Ya, for this I would look at the Clutch tamer(did I say that? LOL).  What could it hurt?  It basically slips the clutch for you, which is what you need.  I have no personal experience, but have done some reading on his website.

A narrower tire is another good idea, but maybe the Tamer is a better start?