It is good that you have gotten him out of an unpleasant situation.
But to be honest: maybe he would be better placed now through a helpful and responsible rescue?
The world is full of thousands of dogs that need homes, but going into a home with many other dogs is not always a great solution or an improvement for the dog-- and honestly, usually is NOT -- especially in a situation where, as you say yourself, you both needed to think 'long and hard', which suggests that in your hearts, you already know this is a questionable solution for this particular dog and for all your others, who now must adjust and lose some more of your attention. Nine dogs means even if you allocate the entire working day to the dogs no given dog will get more than a few minutes every hour. Adding another dog into a huge gang can be quite stressful for all involved whether expressed or noticed on the surface or not -- people and especially, the dogs, who now must reposition every one of the other eight relationships -- and also who now get a much smaller fraction of individual attention that every dog needs daily
. I think any time an addition requires a hard think, it is really a sign that maybe if all are really honest there would be an acknowledgement that a newcomer would be much happier as a single dog or in with another companion or two in a different home -- and really shouldn't be squeezed in because it was primarily felt the original home wasn't suitable. For many dogs, they will actually have had a better quality of life as a single dog in a home that didn't do a lot with them, than they would as just one amongst a massive pack where they just follow all the other dogs around most of the time and get just as little and very likely even less real, quality one on one daily interaction with their new situation. But think how loved and cared for such a dog would be in a new home that really wants its first dog or a companion for another dog.
I know you have added a number of new dogs now in relatively short order, so it might be a good moment to take time to honestly consider the impact for the dogs. :flwr: And also the financial impact if, as is likely with such a large group , you are (increasingly) faced with SM and MVD. MVD is a guarantee, SM is very likely to become symptomatic in at least one (given that I have three with SM symptoms in a group of 5, and 2 of 5 with advanced murmurs). Medications and vet visits quickly become very costly.
You would have no problems getting help to place this new one.
There are huge waiting lists via rescues and breed rescue in the UK. It might be worth thinking this through carefully on whether the best quality of life for this newcomer or your existing dogs is gained by having a ninth be one of a huge pack, or perhaps instead giving that dog a chance to be a much loved solo dog in another family where it would get 100% focus, and where you can rightfully feel you have done great work by helping a cavalier find a great new life. Rescue doesn't -- and I think shouldn't -- be seen to require taking in dog after dog into one's own home (and this truly can become damaging to the existing dogs and no benefit to the later arrivals). The generosity of spirit of rescue often comes in helping a needy dog move on to find a special place where it can be cherished alone or with a pal or two.
There is no shortage of homes for needy cavaliers.