Did the vet prescribe any pain meds? If you can find a pain med that works well with few side effects, it may give Kitty enough relief to give your husband the time he wants with her.
When we've faced this decision in the past, quality of life, not quantity of days, takes on primary importance. Each day becomes a blessing and a precious gift. Every morning we ask ourselves the question, "Are we're putting off euthanasia for our sake for for hers?".
If she still takes joy in her surroundings, still eats, still plays, still purrs, and seems comfortable, then perhaps it's not time yet.
If you find, instead, that you're putting it off because you
can't live without her or would miss her too much, but she's obviously not enjoying Life any more, then you need to take a deep breath and make that difficult decision.
When it comes time, if you make the decision with love in your heart and Kitty's best interest in mind, you can't go wrong. And if you can find the strength to be with her to the very end to help ease her way across, that's the greatest gift you can give her.
I'm so sorry you and your husband are going through this.
It's never easy and my heart goes out to you.