Someone is free to correct me if I'm wrong.
The archival footage of Howard in IM2 that has little Tony in the background I believe is supposed to be from 1974 (I'm at work so can't check the film myself, but I want to say there's a clapper board used that has this year on it?) - not 1977 - so Tony would've been 4-ish (granted, the kid playing him is probably older than that...but given that it's such a short scene, I think that can be forgiven).
We do know Tony was born in 1970 or 1971 - the year on his SHIELD file from the Captain America deleted scene where Steve is looking at his file in Avengers has a 197? year but I can't recall if you can tell if it's a 0 or a 1 on the end (like I said, I'm not at home and so I can't check).
Howard's file in the same deleted scene also has his birth-year, which is listed as 1917 - so you're right on that one. I believe that file also has his death year which is listed as 1991 (same as the newspaper in the 'award' montage from the beginning of the first Iron Man movie)
edit: I know this is a fan made timeline, but they really have tried their best to take first information found in the films found in the tie-in materials as a secondary source and tried to make sense of it all: