Now, the part where he tried to coerce her into saying it was welcomed and she was fine with it, that’s where the real punishment should come from.
According to the article the potential maximum punishment for coercion is one and a half times the potential maximum punishment for sexual assault.
They arrived at the 30 month figure by adding the two together. Given that ratio and the circumstances, I think it's likely that the bulk of whatever sentence he does receive will be drawn from the coercion charge.