The Colts aren't in a position to force anything. They can't exist without the cap and the revenue sharing that comes with it.
I think Polian is rolling the dice assuming a deal will get done and he's trying to get his guys off the market before the rush erupts if it does. If a deal doesn't get done it won't matter as the Colts window will slam shut.
As for the cap, they were right up against the assumed $93.5M as of last week. But you don't have to be under it until next 3/3. They will get under by charging Peyton and Marvin's $19M in 2006 roster bonuses on the old credit card. That alone will open up about $14M in cap space for these contracts, at least one more FA (but not Edge), RFA's, FA (though Polian seldom signs any) and draftees.
As for the standoffs, the union can certainly refuse to sign a deal that is already reportedly done and gave them the % of Total Revenue they supposedly wanted. Would be tough to explain this to it's constituents though once the checks stop coming. And the haves can hold up a new revenue sharing formula that gives the have nots the bulk of their revenue. It only takes 9 votes to kill any deal. But that alone won't stop a new CBA unless Upshaw cares more about power than money. I suppose the have nots could likewise nix any deal that doesn't give them that big chunk of the haves revenue, but since most of them can not survive without the revenue that is already shared, let alone in an uncapped league, that would be committing financial suicide. Franchise values would drop like a rock as well, so it would be like trying to sell your house after the nuclear contamination was discovered in the nearby wells.