Moved here from Piecing...

[Freckle6]

I don't think you're unreasonable to want primary custody. IMO even, it's what's best for your son not even taking into account your H's abuse and possible drug abuse. You've been his primary caregiver for his entire life and he is still a very little boy--almost a baby still. To disrupt that is not good, IMO, and shuffling him back and forth 50/50 is not a healthy way for him to spend these formative years.

And i don't care what dirt your husband can make up about your fitness as a parent to fight you, he moved out of the family home and left S in your care. That right there is telling that he trusts S to be in your care.