Glad to hear things are improving - just wanted to add my thoughts that a chain lead and also Shona's suggestion of some training on walks is a great idea

Just wanted to say about the extending lead, they do teach dogs to pull....

Good to hear that you are getting progress. I was going to say you don't need to pin him down, but instead either ignore (but walking quickly with no eye contact is the same so that is good) or give him a counter command e.g. when Tonks was a pup and tried nipping my legs as soon as i walked across the lounge i would stand still, give no eye contact, until she left go, and then ask her to sit (lucky for me that she felt biting my trouser leg and sitting could not be done together! )

Chain leads do work for this but i don't like using them as you can't control the length of the lead so well as it hurts your hands, especially with a large or strong dog, that's why i would use bitter apple sprayed on the lead instead. (always spray it on the lead away from the dog before you attach it, incase they take a lunge at it and get it in their eyes.)