Let's get some facts about Kubica straight.
According to his website he has four sponsors; Lotos, Grupa Azoty (a huge chemical consortium), Pirelli and OMP. Yes, Pirelli is his sponsor, not just his tyre supplier. And I think this was one of the main reasons why the talks with PH-Sport failed. Kubica wanted to drive on Pirellis this year and as you could have seen the tyres allowed him to set great times on Monte. So you were wrong with the first part, but exactly right with the last part.
There is no reason why M-Sport wouldn't want Kubica to succeed. The better results Fords make the more cars they sell and rent.
I think you should check with google about his achievements in his last 20 years in motorsport.