1) I think Haye was concerned before the fight that Wlad would put all of his weight on him in the clinch to sap his energy. They made a point of this to the ref. Haye kept falling in part because everytime Wlad lent on him he wanted to let the referee know what was happening. At times though he seemed to pre-empt the lean and fell before Wlad actually clinched.
2) Haye claims his toe was broken, which effected his balance and his ability to punch. Wlad has always been that way. The Klitschko brothers are avid chess players and this spills over in to their approach to boxing. They take their time and don't make any rash moves. Most of Wlad's world title fights have ended in the latter half of the fight. He breaks his opponent down over the fight and when his opponent has little left, he'll move in for the kill.
Haye still had a punchers chance right up until the bell as far as Wlad seems concerned, so he took no chances. As I said, I think if Wlad wanted to he could've KO'd Haye last night. It's not the way he fights though.
"Let your food be your medicine, and your medicine be your food"