What the hell do you mean "is it falsifiable"? He's making concrete predictions about the outcome of an event that is mere days away. Voters will have the opportunity to select an outcome different from what's been predicted, so it's possible for him to be wrong. Is there some other definition of falsifiable that you are using?
It's even better than that: by looking at his state-by-state predictions and comparing them to election results, we'll be able to quantify his degree of wrongness.
I don't think he has a specific "model" for his "predictions". Reading his recent article, he uses statistics and weights informations gathered by polls to determine the probability of each candidate winning per state. You can't really be "wrong" in that sense, but the actual result can vary due to statistical sampling error, polling error, or bias in the polls.
