New Dog Aggressive to Other Dog Upon Waking

[Deleted]

I'm confused by 'fostering to adopt'. Are you planning to keep this dog or is he going to be adopted out by the rescue you're fostering for? If it's the latter, break him of sleeping on the bed now. Not everyone wants a dog in their bed (I certainly don't). And honestly, if he sleep startles, it's probably not a good idea anyway--the term let sleeping dogs lie exists for a reason. Eventually you or your husband is going to startle him from a dead sleep and get snapped at or bitten.

I'd crate train him in your room at night to start, then eventually graduate him to a dog bed in the same place.