Allison,

So Awesome!!!!!! This is such a good story to hear. I'm glad you trusted your instincts.
What to do next? Formulate a plan and be ready to change it at anytime!!
I think I wanted a manual for my girls, but no one can give it to me. And the one I'm currently writing on my experiences won't work for anyone else!
I think you will know what to do when you get the results from the WJ.
My DD5 seems similar to your DS.
I did put her in kindergarten this year, but it's only a half day. I consider it her public school vaccination. Just enough to get her acclimated, not enough to kill her!
I held my breath and truly expected the worse.
Amazingly, she loves it. We had a little rough patch with the kindergarten teacher, but we've worked it out. DD gets pulled out with 3 others twice a week and she loves it.
I volunteer quite a bit (ie: get a good chance to covertly spy on my girls) and it's remarkable to watch her.
She has this totally focused look on her face, she's all business, trying to figure out all the social stuff.
We're very happy now, but it goes month to month, year to year, teacher to teacher.
So, plan for the best and expect the worst.
You should have all your bases covered, then.

Congrats,
Incog