Js surface problem

About a year or two ago, we used to go to Petco a lot to shop. I made one mistake. I would always let my little brother carry Jasper's leash as we would walk around the store. When my brother would want to run to another aisle, he would pull Jasper on the leash. A problem occurred. When Jasper was pulled, he would slip on the slick surface. This has now made him very frightened about slick surfaces. So, anytime we are in Petco, Petsmart, or a place with shiny looking floors, Jasper will dig in to the ground and sometimes even make himself slip. So, today I have started a training plan. This is day one.

Day one: I took Jasper to Petco. I clicked and treated him when we first approached the store. I then waited for eye contact. This assures that he's comfortable.  We moved to inside the store. I clicked, but j wasn't concerned with his reward. We stood there until he felt a little bit more comfortable and I fed him. We clicked and treated for just standing there. We had a lot of distractions which made things harder. A man had a long aquarium bulb he was pointing at us while he was asking questions about Jasper. His kids also tried to approach and shied away multiple times. I was using kibble. Generally a high value treat doesn't seem to change things with him but next time I'll try this. 

When rewarding, he was biting down hard, which indicated he was clearly worried. I feel like there was some progress made. He was able to walk a few steps without hunching down too much. After a good four or so minutes, we left. That's all we planned to do this morning. We will try again tomorrow.