Sorry, my mistake, it ws indeed his shoulder. However the assassination technique did not kill it's target, this would say to me that it failed. Even more so when all it did was get gaara mad and have him go demon and what not.

I know lee was injured and not moving as fast as normal HOWEVER he also opened the first gate, we don't know how much of an boost this gives him.

I may not remember completly all of gambunta's fight but I thought it was because gambunta was a little scared of him?