My 2 cents
Pretty much in order they appear.
Length/Wings : A bit on the small side, they are roughly the same as the Russian I-16, which means they may not scale to the picture.
Wing Area: At 350 for 6,400lbs, the wingloading is slightly low at ~18.3lbs/ft2. Some like the Italians and Japanese went for low wingloadings, but there is both a weight and drag penalty. For the weight, you might try a 290 wing for a 22lbs wingloading or smaller for higher
Supercharging: You have the engine with sea level performance at 2,500 feet, which is quite a constraint. 5,000-9,000 is reasonable for the mid 1930s.
Cruise speed : Your cruise speed is equal to your maximum speed. This both requires your engine to work harder, and gobbles fuel. Try reducing cruise speed so that the throttle number is between 40 and 80%. Your payload should increase.
Engine data: The large propeller gives both higher horsepower and greater cross sectional area. You are using a high bypass to then constrain the engine output. Try reducing the propeller to about 8 feet and you can then lower the bypass as well.
Engine weight is extremely high for the output. At 0.38hp/lb that is a very poor engine for the time.
In contrast, the 1932 R-18303 Twin Wasp had 775hp / 1,162lb for a 0.67hp/lb output, and was only 4.2 in dia.
Another comparable engine would be the 1937 Gnome-Rhone Mistral Major 14N 970hp / 1,300lb which was 4.3 dia. and had 0.74hp/lb
One could postulate that a 1,095hp/ 1,560lb engine with a 4.4' diameter and 4.6-4.8 fuselage would be reasonable.
Wing ultimate G load : The notes portion of planebuilder advocates about 10+gs for fighters, which this appears to be. The loading used might be acceptable for level bombers.
I may want to edge the wing thickness down some, not crucial.
Fuselage diameter is fine, could be adjusted down slightly, but not important.
Form however would appear incorrect. A "0" is a teardrop, which might fit an A-4 skyhawk, but not a mid 1930s radial. Something around the 0.3-.4 area.
Cross sectional area :5.7 seems high for a cowled radial, which is what your picture has. That may be related to the 10' propeller blade. There should be a suggested number next to the input. Alternately, the engine tab has both cowled and uncowled numbers displayed.