That is an eastern milk, if there was any doubt. I've kept them, and babies are tiny and notoriously tough to get on unscented f/t pinks. I do not think the snake will "imprint" on pinks and have any tougher time if released after some meals -I just think odds are low it will take pinks in the first place. I've never heard of a lizard eater who wouldn't gladly switch back to lizards. As for legality, that is your decision. I would not feel right about taking a rare species such as that out of the wild permanently, that's akin to killing it from an ecological perspective. If you choose to give it a couple of meals then release, I see no harm in that. But if it doesn't take pink mice, and most don't, you are only keeping it away from food by keeping it captive. Good luck with whatever you choose, and keep us updated.