Isn't it just the remainder of his contract he needs to pay, so somewhere in the region of £40-50m? Could he threaten to do this, as a way of forcing Levy to accept say an offer of £80m from City?
As others have said, he'd have to go to court (and there is zero chance it gets resolved pre window closing)
Does Kane really want to take Spurs to court? for a year?
And if you were Kane, if City/United/Chelsea really want me, pony up the money, if someone put £140M/£150M on the table and Spurs said fudge off, he could push. But if it's the flimflam we are hearing which is take some cash and a few players we don't want anyway .. why would Kane push on his side?