At 8 weeks he may be too small for a harness but I'd see if you can find a harness to fit him. If not now, you're definitely going to want one in the future. As for him not walking on the lead, I would put it on him and try to get him to walk around the house with it to get used to it. You will probably have to give him a few small tugs at first but I think he should start to get used to walking on the leash. That's my opinion at least.