if you have money to spend, I recommend the Mcguire Program. it's expensive, and requires at least 3 nights in a hotel. intensive 3 day workshop will work on the fear of stammering and the physical causes. 100% worth the money. it's a life changer. part of it involves speaking to 100 strangers, after 2 days of training and confidence building. I think your slt was on the right lines, but did not give you the tools to do it.