The only thing that I want to say that might be wrong is that Scott manly (I think it was him) stated that when matter and antimatter collide it also produces neutrinos (?) (some particle if not that) that take several meters worth of concrete to stop. So the reaction isn't 100% matter energy conversion, but its close. Cudos for the work it took for this, I really look forward to reading them when I see them.
While true that not absolutely 100% of the mass is technically turned into energy, the mass of the released neutrinos is so vastly inferior, (plus they eventually decay into photons anyway which is energy in the conventional sense) that the reaction is for all intents and purposes, 100% efficient.
Even at this scale, the mass of the neutrinos released would be unmeasurable. Basically, less than the mass of a quark
Interesting fact: There is a ring of antimatter around the Earth that constantly replenishes itself. Anti-matter circles around most of the planets actually.