Yep. That's manipulation.

He was stewing for a couple of days and now, when you have stuff to do, he suddenly "needs" you. No he doesn't. He just wants his mommy, ie. You.

The correct response is: "Nope, I'm going. I've received no support, so I have none left to give. Call this [hotline], I have somewhere else I need to be."

If he chooses to escalate to actual selfharm, you call emergency services for him. You'll either be getting him help he needs for a problem beyond your ability to deal with, or you'll be calling his bluff. Both is good.