I agree with most of what you said except that Israel DOES want Assad to be toppled. They probably have a puppet picked out to replace him. There is a rush now because Assad will not let Israel launch an assault on Iran from his country so they must have someome amenable in power.
UN: Gaza could be 'uninhabitable' by 2020 if trends continue (AP)
from the article: The UN must find a Goldstone for Syria