"If I remember right, based on spectral data it was speculated that Phobos was a captured comet, while Deimos was a cpatured asteroid. This impact history for Phobos shoud result in throwing some light on that, as well as the time of Phobos' capture by Mars."

If Mars' moons were captured wouldn't that indicate that smaller rocks have also been captured by Mars?
I think a simplier explanation is the moons were formed from impact ejecta. Think of it this way, most people accept idea that material from
Mars gets to Earth- what wrong the idea of some of the material not leaving Mars' orbit and evenually forming into moons.