Cedar -- Wow! 6 grandkids? You have riches of the best kind! Grandkids! Awesome! I loved reading your and their backgrounds. 21 is your eldest? Incredible. And you homeschool-taught Algebra? You go, girl! I'd find that a little intimidating at this stage (algebra memories fade oh so quickly! LOL!). I thank you so much for taking the time to introduce me to each of them, individually, so I can have an idea of who's who when you speak. They are so lucky to have you!
Just re-read some of your paragraphs -- your details on guardianship, homeschooling, cutting your granddaughter's cord at birth, etc. You have quite a story to tell, Cedar. You are a strong one, indeed. Strong-hearted and soft-hearted is the best kind of combo-blend.
So sorry to hear your difficult child has a twisted sense of connection around so much. But especially around you. He is missing out. I don't understand why so many choose to do that, it seems. I once had a psychiatrist tell me that our difficult child "acts out" that way because he trusts me." My response? "Welllllllllll..........that's fine and dandy for him, but not for me!" LOL!
Ahem.... and I reiterate....... You are still a sage soul in many ways! It's a please to "virtually" meet you. 
And, oh, yes.... 4 yrs old is so much fun for our grandson! Long story (for another thread, another time), but we are also blessed to be invited (by our daughter-in-law's siblings) to be "honorary grandparents" to 3 other beautiful babies (ages 3, 6 mo's, and 5 mo's). Lots of babies in our lives nowadays and we, who never bore a biological child of our own (miscarriages, then adoption of difficult child at age 6) are ENDLESSLY THANKFUL for this bounty of beautiful children blessing our lives at this stage. We are KEENLY aware of what a gift we have with these grandchildren (and they all came to us via difficult child's choices.........SO WE ARE GRATEFUL!). We love them deeply! And yesterday was filled with playing in the ball pit at an indoor jungle gym.........just me and a half-dozen 5 yo''s or so.......WHAT FUN!
Blessed, blessed, blessed!
I'll have to check out that "Mean Adult Children" thread
PS -- Love your "Mr. Grandma" story!
Gotta go............My Seahawks are on now!