dan, do you live in the northeast? i dont know you but your current situation may be mine soon. you are thier father and nobody not even my wife will get away with my children without a fight. you cannot for the kids sake allow her to move away with them and gain sole custody. FIGHT MAN use the elders, free legal counsel, family, anything tell her you made a mistake you will talk to elders and repent and if it works good for you. let her think she is in control if that is what it takes to get the kids back in your life. use the time to set a plan in motion secretly securing yourself financially and legally then take action when you have had enough( sounds like she has done this to you) and do everything you can to gain at the very least equal custody. you cannot let her brainwash your babies or worse demonize you in thier minds.
wish i could take you out for a couple drinks proper, but i swear i feel you and care for you, a complete stranger.
take a moment and compose yourself, this is just the start