Quoting Mrs. Mommy to 6 ღ 33:" i feel like i let my son down i just came from an early dinner with him, his dad and his new stepmom ... [snip!] ... what would you do? and why would you do it? idk, i might find a good enough reason here since my mom isn't helping me at all."
Let him go live with his dad. You have so many kids and he will get far more attention at his dads and if he is happy there and taken care of then there's no reason he can't live there.
And you don't know his dad's type. You were (past tense) but people change. My husband now is completely different then my exhusband and I'm a complete 180 from DH's exwife.