Hi and welcome to Yt. I would probably get him used to a leash asap. Even if you just tie a ribbon or string to the harness, it will be a leash.
As for potty training, I use pads as well as take them outside. We boat and our schedules are all over the place so the pads are great. Hubby has a pad down in his garage and will take the babies "out" several times throughout the night and when the weather is terrible. It's so nice to be able to do that when it's pouring down rain or snowing.
Good luck with training. You will be surprised at just how fast Gizmo will take to it.
