I don't know what their kill ratio was but I understand the Dutch did pretty well with them too. They flew with half loads of fuel and ammunition which was fine for point defense missions.
Keep in mind the Dutch and Commonwealth squadrons in the DEI, Malaya, and Burma were outnumbered and were worn down through sheer attrition. I also read somewhere (I need to find the source) that at least some of the Buffaloes in Malaya had commercial grade engines instead of military grade engines which meant they could not stand up to the abuse of combat flying as well.
And that gets me to my next point. The first thing you need to do is change the management at the Brewster Aeronautical Corporation. The company was very poorly managed and had fraud and corruption problems. Management actually decided to shut the company down in 1944 after severe financial losses. Think about that, an aircraft corporation that could not turn a decent profit in the middle of a global war.
This last paragraph is the biggest fix possible. Brewster was so badly managed the FBI actually went in looking for enemy agents committing acts of sabotage. They couldn't believe that it was simply the company's utter incompetence cause them to send out aircraft that the Navy had to virtually rebuild after delivery.
Next is put the aircraft into a combat enviroment where its many shortcoming are less of an issue. Finland is a near perfect example, combat at low/medium altitude and in cold weather. Hot weather robs engine power, the Buffalo was an utter pig over 15K in any circumstance. The Soviets fought their air war differently than the West. Their wars were low altitude almost exclusively, rarely getting over 15K and mostly at 10K or below. Keep the Buffalo in that scenario and it will be remembered very differently (much as the Soviet perspective on the P-39 is the mirror image of U.S. forces that used it in the South Pacific)
Finns did it already. Their version had a lot less weight than the USN version. They also were using better tactics 1941-42 than the USN pilots used in early 1941, or the Commonwealth and others in Pacific/Asia. Other than the Finns and a few hundred USN pilots the ilk of the Buffalo pilots in early 1942 were rookies without a lot of flight time or advanced training. Against the superbly trained Japanese naval pilots of January 1942 & their modern state of the art aircraft the Buffalos of the Pacific battles were going to look bad.
I would profoundly disagree with the statement that USN fighter tactics were notably inferior to those of the Finns. The Finns fought an opponent who played in the F2A's wheelhouse and did it in an ideal weather environment. As you note, the Finns were able to pull several hundred pounds of equipment off their Buffaloes, something that made a considerable difference.
I would also note that those supposedly inferior USN fighter tactics allowed the American pilots to extract a POSITIVE exchange rate with the admittedly superior A6M while fighting in the ZERO'S wheelhouse when equipped with the F4F-3 (hardly the stellar fighter of the war).