Better to get two IH than none at all. I think the first IH is the 1856 (1857,1858)Flying Eagle that they classify as IH, since they are all grouped together in the Red Book. You might be correct as the first HEAD DRESSED IH. Congrats on your finds.
Flying eagles and Indians are sometimes grouped together simply because the flying eagle had such a short run, but 1859 is certainly the first year of the Indian Head. Now you just need all the years in between!