As for the “see you around kid” line, I’ve personally took it as a continuation on how Han will always be “haunting him” since his murder. In the same way with Luke since Luke “allowed” Kylo to “kill” luke (Letting him strike him with the lightsaber).
In essence, Luke knows Kylo is still in the “half in the door” of going totally dark, so his choices (Killing his Father Han or SYMBOLICALLY kill Luke) will continue to haunt him.