a) Garrus' father - would he ever approve of Shepard being with his son? Only if Paragon, or never? Would whether Shepard accepted Spectrehood in ME2 have a factor?
I think he would eventually. I could see some definite resistance to the idea, but if he was such a respected Officer on the citadel (a very multicultural place), I can't imagine him being some crazy speciesist. However I definitely see some resistance, because while I think he'd probably be okay with Shep being human (unless he was really counting on grandkids) I think he'd still have a huge issue with her being a spectre. And I think that would even depend on whether she was paragon or renegade. I think paragon Shep probably has a better chance of approval than renegade shep since she plays more 'by the rules.' But even so, tough to say. I also agree with everyone else who wants two parents present!

How do you think Garrus would respond if his father disapproved of Shepard/the relationship/Garrus fighting alongside Shepard?
Probably like he responded to everything else his dad wanted, considered it, might try it but would probably wind up sticking with what he wanted personally. I could see him having a little bit of inner turmoil about it, but Garrus matured a lot in ME2. In ME1 he seemed pretty impressionable, not so much anymore.
c) How do you think paragon or renegading Garrus will affect how he is in ME3? A little? A lot? How do you want it to play out?
I don't really have much of an opinion on this. I simply expect Garrus to act a bit more paragon or a bit more renegade. How it plays out would depend entirely upon the events of the game.
d) Do you think we will be able to recruit races against the Reapers in ME3? Would do you think about that? Is it too much like Dragon Age?
I don't particularly care if it's too much like dragon age. I'm pretty much open for anything in ME3 honestly, just so long as it's GOOD.
e) Elevators or loading screens?
I play on a pretty fast PC, so I prefer the loading screens since they take all of three seconds (my longest load screen is not a load screen... for some reason my computer has to seriously think before taking me to change my weapon load out). I also want more dialogue though. If they had lots of NPC dialogue to fill the elevator rides (even if you keep only using the same two people.. I'm so guilty of that) then I would be perfectly happy with elevators. But I don't want another massive elevator like the Csec to Normandy one, especially when I practically only ever heard the one NPC dialogue. I think they could probably make it up as a cutscene of sorts. Have it required for 360 where it seems the loading is actually decently long/necessary, and allow you to click out of it on PC, so you can watch it if you'd like, but if it repeats or the dialogue stops then you can just move on.
f) If you could have designed Garrus' DLC armor, how would you design it?
I'm quite okay with Garrus' DLC armor. Although I like the loyalty armor better. Although I use the DLC armor because that armor doesn't have a hole.