
First of all I'm sorry for your loss - 9 isn't any age although it might be 'the norm' for Elkhounds? Anyhow, over the years with our lot, we obviously had comings and goings and really the only one I noticed any reaction from them over was one little bitch we'd kept after very early on she had to have an eye removed (abscess right in the back which we didn't know about until it 'blew' and the eyeball had to be removed - nasty). I'd never shown her (obviously) nor taken a litter from her. She was just 'there'. Clearly she was a force within the pack as after she went, nobody moved onto her place in front of the fire, for quite some weeks. It was as if her presence was still there. Otherwise as one went, another one, or two, was born to fill the gap. It was quite different when, down to the final two of our bloodline, brother and sister, we lost the sister. Obviously finding himself as the sole hound when he's always had others around was bad enough, but he was extremely close to his sister and as a result was devastated to the point he started challenging any strange dog who approached when out on walks. Hackles up, low rumbling and totally untypical for the Basset and him. Obviously he'd been used to standing back and letting the others sort out any problems but finding himself quite alone, was more than he was able to deal with. Seeing this, and actually not liking only having one hound ourselves, we set about finding him a buddy. That took 4 months, booking to arrival with us by which time he had pretty much settled down. We had to take him everywhere we could with us, but if he couldn't come along, basically we didn't go!
Clearly your Jackie X will be picking up your vibes so try to keep his schedule as close to normal as you can in that. Jackies are intelligent little people, but can be noisy. He is into puberty and losing his companion at this time could be a double whammy for him. I sympathise re yapping because my Whippet (yes, we switched breeds after losing our second last although it wasn't totally successful and we now have another Basset!) does the same. I'm not used to yapping dogs but I've tried all I know to shut her down - she's now 7 - to no avail really. With 'asking to go out', I have never waited to be asked. I dictate when there is a need to empty - based on them being on a regular schedule (feeding). So in that, I'd not wait. If you know how he is, when he 'goes' (BM), get him out.
And depending on how you/your family feels right now, perhaps starting a project for a new companion for him might be worth considering. Dogs do grieve, but some more than others.