Tobias Full Name:
Richard W. Tobias
(extracted from Britonia Armed Forces Database)
Juni, classified, but I'd assume she's in her early-mid twenties! You can make her 24 or 27, nobody will care about the difference (well, just don't make her too old or too young in your stories).
I'm not sure about King, but I imagine that I heard his rank in the beginning of the game, when Juni first introduces him. If not, and there is no clue on what his rank or age is, be creative and assign him a rank (ps. I think he's either in his late 20's or early 30's).
Yeah, there is not much more than the game gives on Trent. Most important about him is that he's a man that resembles Han Solo in many respects (not too witty, but courageous). I didn't check the notes taken in the beginning of the game (pre Freeport 7 destruction), so you may as well check that (besides it may revial other info).
Don't forget, a considerable portion of the story is only revealed after completing the main campaign (check especially uncharted systems).
If you've started from scratch, I'll ask you this question: "What happened with the Hispania???". Only once you actually played the game to the point of having an answer to this question (and I'm in the belief you can only get it at a very specific point, beyond the campaign), you'll have all the information you need
Hope I could help somewhat,
X4C-01 out