Hi ,so sorry you are going through this it is heartbreaking
, I went through a similar situation with our dog who was very much like yours an alpha dog who was comfortable in his own company, it’s a running joke with us that some dogs think they’re human but ours thought he was better than that .
It started with a limp that turned out to be a tumour in his leg , we went to what turned out to be the worst money grabbing vets ever ,they convinced us to have his leg removed and a follow up of chemotherapy which would give him 6 months minimum, like you we couldn’t bear to lose him and went ahead , they let an inexperienced surgeon operate and didn’t keep us informed , ten hours later they rang and said pick him up , the bill had trebled but we still thought it was the right thing to do , his leg was healing after a week and he was running on three legs but he soon went down hill , in my heart I knew the dog I’d looked after for 11 years wasn’t right we slept down stairs with him , back and forth to the vets they kept saying different things , kennel cough etc , after 20 days he went down hill very quickly , we couldn’t get the vets to answer our calls and booked him in an emergency vets in the city , but I laid with him and knew he was dying so I stayed with him and he died with me and my daughter stroking him ( I’m still tearing up writing this after five years ) .We got the Royal college of vets involved and found out the surgeon knew the cancer had spread but didn’t tell us ,they also lied and changed documents to cover their tracks .
with hindsight we would never have put him through the operation, we were never offered the option of palliative care and then being put to sleep when the time came but this is what we should have been advised to do which it seems your vet has , you know your dog better than anyone and I’m sure even though you would love to have him around for much longer you would not want him to suffer in any way , I’m sure you’ve given him a good life and you will know when he’s had enough , we have another dog who grew up with him and she’s now 15 so we know she won’t be around for ever , she has lumps and bumps all over the place but nothing that’s bothering her , she’s happy ish she still goes out and likes fuss but there won’t be any operations or messing with her now she doesn’t like the vets either so why upset her , it won’t be easy but we will lose her one day but this time it will be done right not trying to hang on to her for ourselves .
ps our old dogs ashes are still in our living room because none of my family would let me scatter him because they didn’t want him being alone .
Bloody pets they break your heart .