Fbref.
Though they do also have an xAG stat (as distinct from xA) which is slightly closer to your numbers (7.1, 9.1, 6.9). And in fairness, as I look at the definitions that stat does look more relevant when comparing to assists.
Even with that though, I think the key takeaway is that Kane's 14 assist season was an outlier. You're more realistically looking at an average of approx. 7 or 8 assists from him a season, assuming he maintains the level of the last few seasons.
There's also a question as to how the change in team dynamic would impact that sort of relationship. By which I mean we're simply not going to funnel our attacks through Kane/Rashford to the same degree that Spurs did Kane/Son, as we have other creative outlets like Bruno and Eriksen in the mix that Spurs didn't.
And as I mentioned above, that Kane/Son dynamic was heavily transition dependent, in a side that averaged less possession that we do. We're trying to move away from relying on that sort of counter attacking football, so that Kane/Son attack isn't one to emulate.