I've been thinking about it, but I don't really know how exactly Malcolm could have played it differently and achieved a better outcome, especially if his goal really was to get rid of Phillip.
He had to stir the pot, keeping the second idol hidden wouldn't have done anything to change the 7 splitting the vote. Of course if he'd known about Erik's vote, he could saved the idol, but that's hindsight.
I don't think "selling the vote" would've worked. He could have threatened Andrea or something for example, but I don't think anyone would have agreed on any deal in the open there.