C..
Please do NOT Leave the state without telling your son's father if you have a custodial decree. You can be charged with contempt of court and it can cause ALL sort of problems.
Your custodial decree should spell this out. This is a legal issue and is usually straightforward. So, consult your decree or the lawyer who represented you.
PROBABLY you just have to give him notice that you are moving and provide the new address. He has a legal right to know the location of his child. Even if he's a shitty dad. Even if he's never seen him.
I also have sole legal physical custody of my daughter. I moved out of state after the divorce 7 years ago and then I moved again 1.5 years ago.
My custodial decree states that I have to provide written notification of change of address in excess of 75 miles from original address to my daughter's father within 60 days of the move date. If that is not possible, I am to notify him within 10 days of the date I made the decision to move.
**My decree states that failure to do so will result in me being charged with contempt of court up to and include reversal of the original judgement. That was STANDARD language in my state when I got custody (7 years ago).
It does not matter if he has EVER exercised his legal visitation right if you have a legal document indicating what is required by law in that state.
He can't prevent you from leaving the state. Not if you have sole custody. However, he can file for modified visitation, which would change the reimbursement amounts. But HE has to file. And he probably won't.
Just send him a CERTIFIED letter with your new address.
Dear whoever,
This letter is to inform you of the updated address of Little Johnny. His address as of <<Date>> will be 1234 etc etc.
Thanks
Mommy.
Then you're legally covered.
Good Luck.