Awesome ! You can give the key switch a shot of WD-40 and hit it with a blast of air if you have a compressor handy, if that doesnt free up the stickiness then there's a chance that the switch has gotten hot and weakened the spring, (happens if one of the switch terminals has a loose or dirty connection).
The dead spot at 1200 is probably because the throttle linkage is a tad out of sync. As you accelerate, timing is advanced manually as the throttle plates open. Everything has to be synced nearly perfectly to obtain a smooth hole shot with no stagger zones.
The clear plastic outer bushing on the throttle cam roller has a habit of falling apart and will throw it out of sync just a bit, you might check that little POS and see if it's all still intact.
Don't spend too much on "decarbonizing" treatments, they are a waste of time/money. Once hard carbon deposits have built up the only way to get rid of them is to remove them manually (complete powerhead teardown). Ring-Free, Engine Tuner, ect. won't even soften hard carbon buildup, so save your cash.