I rather suspect that "£2,500 per day" was dreamed up by some PR merchant. I'm sure the mercenaries are paid pretty well, as mercenaries generally are. Here's a page I found speculating about this kind of thing, and quoting some figures for comparison.

But there's clear no evidence I've seen that Gaddafi is particularly dependent on the mercenaries he employs, or that the Libyan troops are particularly liable to favour the opposition, as was the case in Egypt.

It maybe that the mass of Libyans in Tripoli are hoping for the rebellion to succeed, but I haven't seen any evidence for that. That doesn't mean Gaddafi is a nice man or a good ruler, but all too often pretty nasty and incompetent rulers have a lot of popular support. They even win elections.