Feline Faucitis/Stomatitis + Interferon - Update

Well, we don't seem to be having any luck with the interferon
treatment. See history at thread "Any experience with interferon
treatment for feline stomatits/faucitis?".

Tinin got his first treatment (including a major dental with six
regular extractions and six extractions of teeth with lesions) in
early December. He was doing a lot better afterwards and gained about
two pounds in a month, but I have to attribute the success to the
dental. He had his second interferon treatment in early January and
there was absolutely no response to the treatment. The vet who did the
surgery saw him yesterday and says that he now 'only' has stomatitis
and faucitis with no visible improvement, but no longer shows signs of
gingivitis.

Given that a second dental with extraction of the remaining teeth is
pretty drastic (not to mention that the shelter can't pay for it at
this point), I want to look at some options for an interim. Has anyone
had success with switching their cat to an allergen-reduced/free diet?
Does anyone have a cat which has been on steroids for quite a while as
a result of this condition and how well is that working i.e. is the
cat apparently pain-free?

Thanks in advance!

Petra