Your ketones won't come down until you are able to tolerate foods as well as the fluids they are giving you. Have they not given you any anti-emetics?
I took 6l of fluids with my first admission and was still 3+ afterwards but as soon as the drugs kicked in and I was able to eat something, they started to go down.
They also shouldn't be discharging you with ketones that high and certainly not if you can't tolerate food. Are you able to drink anything on your own or has your hydration come solely from the drip? If it's just the drip then that will also delay your discharge.
As a fellow sufferer, you have my sympathy. I've been where you are. PM me if you need to talk.
x