Well a typical electric oven at full power draws something between 3700 and 7500 watts and you had it connected to a 3,000 watt generator, sure it is a very conservative 3,000 watts, but if you had the oven on, plus those other loads you were way over 3,000 watts.
As to what did you fry, there are a couple of possibilities, worst case and what I think is most likely here is you fried the output windings in your generator end, which for practical purposes means time to buy a new generator. If you are lucky you only fried the exciter rectifier bridge diodes or less likely the voltage regulator. (there are a couple of other possibilities, but only testing will tell).
It seems you kept applying load to the generator until something broke, and it did, generators are generally designed with breakers sized to protect the wiring primarily and then the gernators against a direct wiring short, not a slow build up of overload, the problem is the windings inside the generator head can overheat and fail before the breaker has time to trip on slight to moderate overload.
Ike
p.s. if you had 15% power use on the meter with 2 air conditioners hooked up I suspect something was wrong with the meter, also did you have them both hooked up to the same side of the windings, if you had it in 120/240V single phase mode you effectively split the available 120V loads in half between the 2 output lines, giving each about 1.5 KW worth of power. Connecting 2 1,000 watt generators to the same side during operation would leave one set of windings loaded to 2,000 watts, and the other at 0 watts, so you would be in overload there. I suspect this relatively limited amount of 120V power available in 120/240V split single phase mode is part of the reason it is not officially supported on these 3KW generators.
Paul