You're not factoring in any cap holds here.
It was originally rumored that the salary cap would be $67,100,000. If that is the case, we would have $7,997,083 in cap space (I use basketball insiders for the contracts and cap holds). If the salary cap increases by another $2,000,000, then we have $9,997,083 in cap space to start.
If we make a trade like Landry and removing the 2016 1st Round Pick Protection for a future protected 2nd rounder (basically removing the protection of our pick for instant cap relief), we would have $13,971,990 in cap space ($15,971,990 if they increase the cap by $2,000,000).
If we were then to waive all of our unguaranteed contracts (McCallum, Moreland, & Stockton), we would have $15,034,105 in cap space ($17,034,105 if they increase the cap by $2,000,000).
If we're trying to sign Green, there will likely not be any room for Rondo unless we make another trade for cap relief (likely Thompson).