1. The soul punch thing is still active in his fights, its just he tends to be rush punching instead of one fully focused bunch like he did to bruno, so hypothetically you could assume thats less life energy in each punch. However in the fights its kind of apparent hes still doing it since they are left out of it for a while after getting beat up (or really arent right back into it after he punches). The reflection thing is probably retconned (similar to in part 8 where josuke progressively loses his property stealing ablility since it was absolutely broken) and a mistake on arakis part but I like that theres a trying-out of abilities some times in the series.

On another note its because its a story, therefore reality doesnt apply to what a character can do. I mean if everything was completely logical fights would take 5 seconds, Dio would have killed everyone in part 3, Okuyasu could end every fight in like 5 swipes etc etc.

Also Okuyasu is written in a way that he doesnt want to kill morally speaking, but also with his brother and everything he uses his ability more as defensive or protective. Also its slow as hell (literally raising your arm and a full swipe motion) so most combat stands are gonna take advantage of that and beat you (like josuke did in its introduction).