To add to your list, a few months ago I compiled a list of differences between the FE1/3/11 scripts.
The biggest difference I remember is the ending of Chapter 7 (the Lefcandy chapter), in which Morodof gives some backstory info on the three main dragon tribes. This information was cut in both remakes:
That detail shows up again later on in Chapter 17 (Starlord), where Moses mentions Basilisk in his battle quote but Morzas in DS does not. And also in Chapter 9, where Mannu mentions Salamanader.
Chapter 10 (Princess Minerva) had completely different opening narration.
Jake recruitment in Chapter 11 (Knorda) is a little different (he's characterized as a bit more of a playboy, as opposed to the remakes where he's pretty faithful to Anna).
Hollstadt actually gets lines at the end of Chapter 13 (Wooden Cavalry). Evidently he was in charge of the ballistas.
A small detail, but in Chapter 14 (Gra), Himmler is the one Camus says was hiding the tome. (DS names Volzhin/Bozhin/whatever)
Some dialogue is shifted around in the last few chapters, but is otherwise mostly the same. There are some timeline differences as well that I'll address at the end.
Another small detail, but Camus openly calls Nyna his "beloved" in his death line (this was cut out from all subsequent incarnations, prolly cause of the cheese factor XD).
As Falchion alternatives, Gato originally names the following: Miracle Rapier (as you noted, this is locked to Marth, as Est states during her recruit conversation), Gradius, and the Devil Axe.
Timeline differences: When Nyna is relating her backstory, she gives the timing in FE3 as "three years before", but in FE1 it is only "two years before". (Unrelated note: FE1 Nina refers to Medeus as "Emperor Medeus of Dolhr" as opposed to the "Dark Earth Dragon Medeus.") I can't recall if DS gave any specific timing (I think it didn't).
Similarly, in the ending, FE3 gives the war's length as 5 years, DS doesn't mention the exact length, and FE1 has it at 3 years.
Most other changes were just wording/phrasing differences, or stuff that got expanded in the remakes, plus occasional differences in village dialogue due to gameplay tweaks.