None of the above improvements you describe will do any good ! Those dimmers are good enough ONLY for resistive loads (no inductive or capacitive , NO !)
The problem with those resides in the fact that an inductive load will make a defazed sinusoids ( current behind voltage ) ,and a capacitive load , the voltage behind current , and the command schematic will heratically "find " a zero to detrigger the triac. As you saw on video , the " command" for the triac ( potentiometer , resistances , capacitor and diac ) is supplied via the motor , and there will be a lot of armonics , generated by the tool ,itself ...This , will be translated in opening and closing of the SCR device not in zero , but somewhere on the sinusoidal cicle .., with a lot of heat generated and finally destruction of the SCR's junctions ( do not forget that the triacs are not guaranteed in all the 4 quadrants !)
That's why the schematics for electric motors includes an IC with the capabilities of command ONLY in zero point , regardless the nature of the load...
Anyway , I'm glad that you found a good replacement for the speed controller , and the idea of an additional heat sink is beneficial .., by the way , did you checked the propeller that should be there for active cooling.., maybe is clogged with dust , or is moving freely on the shaft.., I was just saying...
Wow ... I just opened the link you sent.., cool looking machine , and the price seems to be good . Go for it !
See you around !...