some comments on your list..

#7. Don Fanucci -- He was a don.

#8. Don Tommasino.

#9. Don Francesco Ciccio -- He killed Vito's father, mother, and brother.

#12. Don Domenico Clemenza was the actual Don in Clemenza's family, not Peter. It was mentioned in The Sicilian book by Mario Puzo.

Also --

Don Roberto -- owner of the 'ratholes' in NYC during the time of Vito's growing up.

There were some other leaders like Tatagglia, Sollozzo, and Moe Greene who were introduced but never addressed as a Don. Sollozzo and Greene didn't seem to have their own families but Philip Tattaglia could probably be a Don, considering he at least had a son in the business.

Barzini and Cuneo were definitely Dons... and there was also a "Don Francesco of L.A." who was going to protect protect Fredo during his trip to Vegas.

In the third film, during the meeting, one of the men at the meeting is recognized as Don Perisi. Don Altobello is the one who wants to settle everything with reasoning.

That's all I could come up with for now.