"I'm curious about any understanding you have on Orton-Gillingham training (since your son is dyslexic) and how you may/may not merge that understanding with Montessori since there are so many similarities?"
Orton-Gillingham has some similarities with the Montessori approach. My feeling is that you don't need both if you implement the Montessori/Dwyer approach accurately. The sandpaper letters give you the sensory stimulation needed to promote a memory link between auditory and visual systems. And there are so many possible extensions you could do with the sandpaper letters as well as the movable alphabet, phonogram folders, and phonogram alphabets, that the bases really are covered with the Montessori/Dwyer approach.
With dyslexia, I think there are a couple of things we need to do. First, practice the sandpaper letters everyday (just like brushing your teeth). Add in distance and other memory strategies (like keeping the t next to the turtle) to keep it interesting. Next, inspire the children to want to read! Third, read together often, taking turns doing so...and never correct the child for substituting one word for another when they read. (This is actually a great strength of many people with dyslexia; their ability to predict meaning and find a synonym when they stumble over the mechanics of reading a specific word.) Fourth, have patience! Just keep modeling your adoration for the written word, its power, its beauty, and the possibilities it brings to inspire others and influence their thinking. Many children with dyslexia are late bloomers when it comes to reading fluency. But, they get there as long as we are vigilant in assuring the foundations have been met.
I have a dyslexia page on my website that might be helpful. You might also be interested in reading our language album so you can see the full details of all of the language lessons possible according to the Montessori/Dwyer approach to early language learning.
Hope this helps and keep up your most excellent work on behalf of the child!