Before I change default v-sync to adaptive sync that P51 would have been doing the extreme funky chicken twirl snap and flip. After I turned off the game's v-sync and enabled NVIDIA adaptive sync, that P51 is performing what passes for ACM these days when caught low and slow with no options. Pumping his nose into red outs side to side makes him impossible to hit from as close as you were.
Being in a C202, you are in a BB monster plinking at that P51. If you were in the C205, you would have shot him down, unfortunately after expending all of your 20mm. Under the same circumstances in a spit8, I use up most of my 240 20mm. And like your film, if the gyrogastic maneuvering con is at 400, I can land rounds and put an end to it. Your BB monster guns were not helping you.
There is something with 200yds and doing the gyrating funky chicken dance that makes your plane impervious to getting hit. Did you try riding in your P51D's cockpit to view his maneuvering from that perspective. He was simply jacking the nose up and down while rolling side to side. If you had more green guys with you, usually their rounds over your shoulder puts an end the the gyrating con because at best one is 400 from the con while you are 200 or closer and missing.