Welcome to FDMB!
I'm going to link
information on ketones and DKA. Hopefully, this will help you get information from the vet hospital on Stoney's condition. Cat's can develop ketones but not be in DKA. Basically, if a cat has an infection/inflammation + not eating enough calories + not getting enough insulin, there's a good chance that ketones will happen. The ketones can throw electrolytes off and then it's truly an emergency. What I find concerning is that you did great noticing the acetone smell on your cat's breath. That's a sure sign that ketones are happening. Your vet should have dealt with this more aggressively.
I also want to point out that high blood glucose levels are not a sole indicator of ketones. It's far more important that Stoney's lab work is stable and his ketones are at a level that are manageable for you at home. Either trace or lower on a urine ketone strip or below 2.4 on a blood ketone meter is what you're looking for. And please keep in mind that ketones can develop fairly quickly so get supplies and look for changes in behavior, particularly lethargy.
All of that said, there are any number of us who have cats that survived DKA. Mine was one of them. When she was diagnosed, I had two vets tell me that not all cats recover. Gabby did. It's going to be some work on your end to keep Stoney safe and keep him stabilized but it is manageable and we're here to help.
While he's in the hospital, I'd encourage you to get set up for his coming home. Low carb, canned food will be helpful. If you're not sure what he'll eat, don't buy food by the case. Try a few different types and see what he may like. Maria/Corky linked a food chart. The chart had carb levels listed. You want foods that are below 10% carb. Remember, calories are your cat's friend when recovering from DKA/ketones. We suggest 1.5 times your cat's normal calorie consumption. You'll want to pick up a glucometer -- the Walmart Relion meter is fine. It's not necessary to get a pet calibrated meter. The strips are very expensive. You can also pick up any brand of Ketostix at Walmart. Those are the urine test strips for ketones. Also, you'll want to add water to Stoney's food. Water/fluid helps to dilute ketones.
Please let us know how we can help. The first several weeks of learning how to manage your cat's diabetes is hard, if not overwhelming. It's even more so when ketones are in the mix.
@Bron and Sheba (GA) will likely be along. She's great with helping out with ketones.