The jam runs from late March 2 to March 12, but it says that it's from March 4 to March 12 in the description. However, it seems like the main restriction is that you have to spend 168 hours on it. Given how I'm planning to submit my game to two jams, and the other one ends on March 10, would it be allowed to start earlier as long as I only spend 168 hours working on my submission?

The jam runs from March 4 to March 12, so it's not possible to start before. You'd have to intersect the time of both jams if you wanted to participate in both.

Ok