They never give any detail on Quarian ranks, but from what I gleaned through Ascension and the N7 mission with the crashed Quarian shuttle, I believe most crew members of the Floatilla are actually part of the Quarian Navy. They probably "retire" at some point in their lives (I see the Conclave as civilian), but I would say that the bridge crew and operations staff of every ship probably hold active rank.
We've seen that there are admirals, captains, commanders, and lieutenants among Quarian crew, and probably more ranks. I would assume, from his deference and manner, that Kal'Reegar is enlisted (or the Quarian equivalent).
Best guess? Tali isn't a Marine. They would have said so if that was the case. I do believe, however, that she's probably a naval lieutenant. She was put in charge of both the Freedom's Progress and the Haestrom mission, and she's at just the right age to be a junior officer.
Nations like Israel where military service is compulsory don't put as much emphasis on rank as do countries where service is volunteer-only. I can see the Quarians following this pattern. Admirals and captains are rare and are honored as such. Many people probably go from lieutenant to commander during their compulsory 'careers;' because of that, the Quarians probably don't make a big deal about those ranks and never really mention them in casual conversation.