Sounds like Blaze is definitely getting there - doing well on the walk is really good progress, and I'm certain you'll get there together in the end
My trainer is rather biased, as she is a great believer in clicker training, but she thinks that using a clicker is one of the easiest ways to get a dog to stack well, so if you don't already use clicker training, it might be worth a try...
But well done to Blaze on not completely freaking out - what a big, brave boy... Your Mummy is obviously very proud