Things continue to move in the right direction - while we could see positive indicators of engraftment over the weekend, now it’s crystal clear that it’s working. 
You can see from our attached white board chart: 

• WBC = White Blood Cells
• ANC = Absolute Neutrophil Count
• HGB = Hemoglobin
• PLTS = Platelets

Overall WBC count was the earliest sign of things working. 4,000 to 11,000 is considered normal, so at 2,200 Sam is well on his way. 
Within the white blood cells, you start looking for neutrophils, which make up a lot of the immune system - getting to 500 starts the clock here - after 3 days above 500 you’re considered engrafted. Zero on Saturday morning, 270 Monday, 620 yesterday and 960 today. 1,800 to 8,000 is considered normal. Being above 500 tomorrow and Thursday is the most important gate for getting him home. 
His red blood cells continue to hang in getting hemoglobin to the system - a little low compared to normal (13.5-17k considered normal) but fine for now. 
And platelets are getting better quickly - 150 is the minimum normal range; Sam is at 80 today. Clotting!
Assuming no setbacks, Sam getting to a reasonable nutrition profile is the last challenge - he’s been eating more normal foods lately and they’re tapering off the IV nutrition.  
So I would think optimistically we can get home Thursday, but Friday might be more likely. Either way, it would be 25 or 26 total days, which is about the best possible path. I had been mentally preparing for 6 weeks; Sam has done so much better. 
So! Now we are shifting towards thinking about how to get ready for life outside. It’ll take 3-4 months for Sam to get T & B cells, and he’ll be very vulnerable to attackers of all sorts during that time. We’re getting the house deep cleaned, changing air filters, getting rid of fresh flowers, etc etc. Much less controlled environment. 
And Sam will still be coming in to clinic multiple times per week, and may be hospitalized once or twice to fight off random infections (almost everyone comes back at least once). 
For this week, goal is to get him home healthy. Then we can turn our focus to a goal of seeing if we can get him to Paly in August to start his senior year. 
Step by step.