Sharon,
I'm really happy he is doing so well. Try to hold some of this joy in your heart for the next time he backslides. It's a true gift to know he can move forward and maintain this long.
I remember feeling guilty the first time Duckie reacted with tears rather than raging. A mother shouldn't be happy that their child cried, but it was so much more appropriate that I couldn't help but feel a little joyful.
Fingers crossed and prayers said that you get more of the good from difficult child for a long time to come.