What is this?
#2
Not being a smartass, but get some of it on your finger and smell it. That's part of your subframe, and shouldn't be leaking anything at all, let alone something important. Could be grease or part of a cheeseburger you ran over yesterday.
#3
I actually have smelled it. It smelled like grease and no I haven't ran over anything which was that high up the ground. It looks like the previous owner used it as jack point (as you can see in the picture). Would that cause problems?