whistling question

That's alot of info to deal with at one time....lol.
Quickly on the peg-leg in 2nd only is mystery to me, maybe just a fluke.
As far as the noise if the belt has been run loose and glazed it wont matter how tight it is now it can still squeal. Another thought on the noise is what type fan are you running. If by chance it's pump driven and has a clutch i've seen those make a similar noise when trying to disengage at higher rpm.
Tuning wise it's gonna be timing first, carb second. Remove and cap the vacuum advance for now until you get your base timing and curve straighted out. Please post again the timing with no vac hooked up at idle please.