First, when he went to Giles in Pangs. Even if he thought he couldn't hurt anyone (human or demon) at that point, nothing was stopping him from breaking into the hospital at night and steal blood bags, especially considering that Sunnydale's hospital didn't have the best security in the world. If he was worried about the Initiative, he could have left the town.

Yeah there are plotholes. But the writers needed him in Giles' house! Suspension of disbelief...

I agree Spike needs to belong to something, to a group. Despite the punk attitude, he is not a loner but a social being. That's why he stayed in L.A with Angel's team.