Is this the hotel that hosted an AMA convention in the late fifties, where Charleton Heston appeared at the world premiere of "Ben Hurr?". The movie was shown in a new expanded screen format. Gen. Dwight Eisenhower also appeared at the venue.

The convention, yes; the premiere, no: the premiere of Ben-Hur was 11/19/59 at the Lowes state theater in new york city; it might have been a special showing of the 1956 film the ten commandments.

Its also where Elvis sang with Frank Sinatra in 1960

Yes

Perhaps.

Maybe.