Yeah, I think the break was probably because of boiling too hard. I'll have to remember this when I recommend this to others in the future.
I haven't really timed mine. For pulled pork where I have a pretty thick chunk of vacuumed meat, I think I let it go 15-20 minutes or so.
For ribs, it would depend on whether you have them stacked or in a single layer. If they are stacked, I would still say 15-20 minutes. Less if they are not stacked.
To be honest, I don't usually have a lot of leftover ribs, so I don't think I have ever reheated the ribs this way. But I regularly use this method, with Chicken, Turkey, Pork, and Brisket.