The kick problem you describe might be like the one i have. The problem happens when you are pedaling and try to apply the throttle it slams really hard. Pedaling only with no throttle works OK. Throttle only with no pedaling works OK, but if you do both at the same time it gets ugly. This was an issue with a certain vintage of controller firmware. There is no easy fix for the problem.
You can test by using the throttle only, being careful to NOT pedal and see if it runs smoothly.
If you have this problem, the only real solution is to replace the controller part. What I did was disable the PAS by cutting the grey wire so only the throttle works. I am happy with this solution. Alternately, you could disconnect the throttle.
Like any motor, if you really try, you can overheat it. I do a lot of climbing on really steep trails, so I replaced the chain ring with a 30 tooth and use low gear most of the time. I think the internal thermal protection kicks in around 60C. Even on a hot day, the most I've measured is 50C after a long climb. My other bike with a hub motor would overheat way earlier.
"One test is worth a thousand opinions"