Iman's cap hold is 250% of his last salary by rules. Thems the rules from what I have read.
And again, you're ignoring the minimum roster spot cap hold. You have to add another $6 million into it and we'll assume Iman signs somewhere else. That;'s at least $42-46 million depending on the rookie.
Even at $42 million, that's only $18 million roughly in cap space.
In order to sign 2 max contracts at a combined $30 million (low end), you'd need to have under like $22 million in salaries total.
Take the Lakers. Even if Nash officially retires, they renounce the rights to everyone and only Kobe and Sacre, Kelly, and Marshall stay at their salaries ($26.5 mil total), they don't have 2 max roster slots. What makes you think the Knicks do?
You have to understand how cap holds work. Empty spots have a cap hold! The cap is $60 mil, not $70 mil!
This is not legal! Rondo would have a cap hold of about $15 million or something! Him and Melo along with JR would be enough to deny you of a single max slot, most likely.