Just leave him. If he's hungry, he'll eat, no matter how long it takes. If it gets too cold, and he decides not to eat, or he's not actually hungry, he'll let go and slither away. May scatter some rat-stuff as he leaves, but you'll be able to clean it up with some paper towels and spray (we use the chlorhexadine here).

We've had a few rats pop in the past. Whether thawing the XLG in the room overnight or using hot water. Some of our snakes are very aggressive hunters.... very hard, fast strike (sometimes even before the rat gets close enough) and very tight, hard squeezes.

And too, like the earlier poster, if he's in such poor condition, he's very likely dehydrated and you'll want to go smaller prey for a few feedings so he's less likely to regurge. I've had to do that with a couple of our rescues.