I've made a lot of progress in the last couple of days.
First, I found the Saab trouble code list that shows that if LTFT goes over 25, a CEL is thrown. So 25 is the upper limit for this car.
And I now know the relationship between LTFT and ethanol content. Is is y = 0.54x - 4.6. y is LTFT, x is ethanol content.
With these two pieces of info, I now know that I'll get a CEL at 54.8% ethanol!