Follow on from multi dog household fight

Thank you again for all your replies to my previous thread.
However I'm after advice again! Norman my elderly greyhound who was the one who got set upon has healed physically (the bruising on his side has almost gone and little wound on his back which I think was where he was knocked down on the concrete is healing well) but mentally it has obviously scared him. The bullmastiff bitch who is the one who started it has been fine with him (from what I can tell) as have the others. Norman has now been spending nearly all his time upstairs on our bed (now this is not completely out of character as he does like his comfort and to keep out of the way of the younger ones) but normally he will come down during the day. The last few days he only comes down for the toilet when he's desperate and then goes straight back up, even been having to take his breakfast up. Yesterday he wouldn't come down for a walk either. The thing is although my husband who loves the dogs it's always me who feeds, walks etc., though hubby sometimes does come on walks but what I'm finding Norman is alot more relaxed when my husband is at home as well, yesterday was the first time we hadn't taken them out together and that's when Norman refused to come downstairs. Is his way of thinking that mums useless and obviously can't control the situation?
My worry is he is really miserable now and I'm not quite sure what to do about it. At this moment I'm in the lounge h other three are lounging around snoring! But he's upstairs, not even been down for the toilet yet
Any advice once again would be appreciated, sorry about the essay again!

He's obviously avoiding another confrontation.

Is it possible to remove the other dog(s) so that he can see them & they can see him, but they cannot have physical contact. You can control the situation this way & build up his confidence.

If my Rjj has a fallout with either of my other 2 boys he gets put to bed in his crate to cool off & he even puts him self to bed if he I catch him starting to wind the others up.