Hello!
Coming up with a name is hard; facing myself that same conundrum, I can only agree.
Anyway, my favorite names among your list are "Nemesis Wing" and "Exile Squadron".
The first one is a pretty cool mix of words and wouldn't be out of place for a space-themed shmup. "Nemesis" is already the name of a few Gradius games, so that may be why the association seems natural to me. Make sure there isn't already a game with that name, I wouldn't be surprised if it already taken.
Exile Squadron reflects the idea of a ship/plane, but its strength depends a bit more on the game's plot, notably due to the "exile" idea. If there isn't an actual squadron that was exiled (but may have had to come back to save the Earth forces against the colony?), it may not be as good a match.
Zander ZX can work IMO and seems rather unique but for some reason I think it would match the game better if it was very conventional in its themes and universe, with alien bad guys in it and a pretty straightforward plot. Here, the conflict seems to only oppose humans so there is more political complexity to the depicted battle than what Zander ZX suggests to me.
As for how I feel about the others : Nexus Gear reminds me too much of the Nexus phones, M-Omega is not evocative enough as Omega is generic and it is not obvious what the M stands for, Myrmidon on its own does not make me think of futuristic spaceships and would be better with another word or two, Echo Guardian would feel more at home as an RPG name, Panzer Suit sounds better as the name of some in-universe technology rather than the whole game's name, and Spirus is not a bad spin on the -(i)us naming but it lacks some coolness factor.
Anyway, those were my impressions!
Oh, and if you have screenshots or videos of the game, feel free to post them as they can also help us see if the names match the game's atmosphere.