SLP working towards my fluency specialization here! Everything you’ve mentioned that you’re doing sounds great! I would also add to spend about 15 minutes a day with just your son where you have special time to play/spend time just with each other (that is if you have other children). You can also get some tips from the Stuttering Foundation’s website and Stuttering Therapy Resources, which is run by J. Scott Yaruss and Nina Reeves, who are both SLPs with their fluency specialization and are amazing. Although many children during the preschool age go through a period of stuttering, there are risk factors involved, so it’s great you are on a waitlist to see an SLP. I don’t recommend the wait and see approach, each child is different and some may require therapy while others don’t based on the risk factors (e.g. males are more likely to continue stuttering as compared to girls, family history, etc.). Hope that is helpful!