I've just been reading through Skinky's thread. I can't suggest much, but my cat had major problems with appetite loss during a pancreatitis flare. It's agony to go through, and my heart goes out to you.
I note that Skinky still seems interested in food, perking up when she hears the can open but she just doesn't want the food. Is she showing any symptoms of nausea, by any chance (e.g. pulling faces or lip licking after food, licking some food then leaving it - there's a good symptom checker from Tanya's Site
here). If she is then Cerenia or GENERIC ondansetron (for price - Zofran (branded version) is obscenely expensive) alongside the appy stimulant can really help. Have you managed to get the appy stimulant yet? If not, then if possible raise merry hell till you get one. The appy stimulant made an immediate difference for Saoirse - she started eating very shortly after the first dose was adminisitered. A tiny, tiny dose of Cyproheptadine was enough to get her eating for several hours. If Skinky is queasy, then anti-nausea meds would help both with symptoms and also with prevention of food aversions.
The only other thing I can think of is maybe because of her sinuses she can't smell/taste the food properly. Things that can help are to put something pungent on the food (e.g. tuna water, parmesan cheese, Fortiflora) and / or to warm the food up a bit so that it releases more aroma. I'm sorry if I'm suggesting things you've already tried. I just want so badly to try to do something to help you and Skinky.
I don't have enough experience to suggest anything about insulin dosages.
I hope that you can get Skinky to start eating very soon. In addition to providing nourishment, it will make insulin treatment more straightforward. I'm going to keep you both foremost in my prayers. ((((Skinky and Mom))))