I have the same motor and approximately the same gearing ratio. I also have a 6S (the amp hour value doesn’t matter for this). A 8Ah in 15C is fine, I think, because it allows 8*15 = 120 A in theory. But in practice, I would never go higher than 80A. But your motor has a lower value for this. I’m also limited by the motors (for the Amp I can put on it). But it allows me to go at 30 km/h (I never ride at this speed. To fast for me. I weight 60 kg, so maximum speed can vary for you).
And finally, I really advise a VESC ! It cost 70$ dollar more. But I lost 60$ because, I first buy an ESC and finally buy a VESC. It much more confortable to ride with an VESC and much more reliable.
If you want to have smooth acceleration with maximum efficiency.
And smooth, dependable, predictable brakes, then get a Vesc.
But if you don’t care about those things, then get a car esc, just don’t try to use your brakes at high speed and always wear protective gear.