Criminal Code of Canada
265. (1) A person commits an assault when
(a) without the consent of another person, he applies force intentionally to that other person, directly or indirectly;
There is evidence that he punched them prior to giving him their express or implied consent. Therefore, if that evidence is to be believed, he committed an assault according to the Criminal Code of Canada.
What happened afterwards, whether they called or texted him, offered him a blow job or whatever is only relevant to their credibility as a a witness. There can not be retroactive consent. There can be forgiveness, but not retroactive consent.
If the witnesses are to be believed that he slapped, punched or otherwise "intentionally applied force...directly" to them, then he committed assault. If it was for a sexual purpose it is a sexual assault.
The only defence I could imagine to these incidents was that for some reason he had good reason to believe that they wanted or liked being slapped around. Like if the text where she said she "loved his hands" in the context of being slapped prior to the slapping... then I can see he might have had a reasonable belief of vaguely implied consent.
Kind of the same as going out on a "date" with someone and leaning over and surprising her with a kiss without her express prior consent. If you reasonably thought maybe you were "more than friends", even if she rebuked you... that is not likely to lead to a conviction for sexual assault.
But he introduced no such evidence of a priori belief that he thought she was into it.
I'm going to predict that the Judge will convict him based on the evidence of the witnesses.