I’m very sorry about your loss of Sweep. That’s sweet that he was able to be with her in her final moments…
I think I have to agree with your husband regarding not getting another rabbit right now. Stanley is getting up there in years and it sounds like he is receiving (or will be receiving) necessary vet care. Vet visits, tests, and medications are expensive AND require a great deal of your time and energy. Being a caretaker to an elderly and/or ill rabbit (or any pet) is very emotionally and mentally draining. With that said, it can also be rewarding to have that one on one time with your pet. My advice would be to focus on him. If he enjoys your company (or even just hangs out in the room with you), he is not starved for attention.
This is a very personal topic for me. We lost our lop in June (he was 8-9 years old) and we chose to not get another rabbit as a mate for our mini rex (she is now about 7 years old). We don’t know what the future holds for us right now (planning/hoping to buy a house sometime in the near-ish future). We want to get a dog when that happens, or possibly before if the right dog comes along. So right now we’re just not making any new commitments.
There’s nothing wrong with waiting, enjoying Stanley, and then crossing that bridge of another rabbit (rabbit pair) when you get there. I like the idea of taking a break and then starting fresh…