My experience is with salmon grilled on a Big Green Egg. I did not wrap the fish in anything, because in my opinion the way to check done-ness is to look at the fish. Details on that experience are below.
The problem with trying to do this "by time" is that there are just too many variables. Did the fish sit out on the counter at all? Are the portions thick? What is the overall density of the meat? What is its moisture content? Does your grill have hot/cool spots? And so on...
I've done actual calculus (being a physics guy) to determine how long to smoke brisket and Boston butt (Newton's Law of Heating/Cooling, if you're interested in the math, it is available here). Even then, I was off by roughly an hour for a 12-hour smoke. My lesson learned was that we have to do these things by temperature, not time.
I have a remote temperature gauge that I use with the Egg. It's very convenient, and cost about $40 at our local hardware store.
Notwithstanding, there are potential answers to your questions, don't lose hope!
1) I have had success keeping my Big Green Egg at 350F, putting the fish (full salmon fillets) skin-side down over direct heat. The distance from charcoal to the grill is about eight inches. The fatty skin will char, but it protects the flesh wonderfully. In addition, you get all those lovely juices flowing.
2) I did four of those fillets, so a total of about eight pounds, and kept it on the heat for 15-20 minutes (one came off at 15, two at 18, and the last at 20).
3) In my experience, wrapping can speed the cooking. The meat ends up being slightly steamed from its own moisture. But this all depends on the temperatures you are using. Although wrapping is good for keeping things moist, it is not so good for being able to tell when the fish should come off.
Solution: don't wrap the fish. If you're concerned about the fish going dry, use a nice marinade. I have found that marinading my salmon in equal parts soy sauce, lemon juice, adn brown sugar. Then, when its ready for the grill, I brush my salmon with equal parts melted butter and real maple syrup - it produces great results. I apply the brush before the meat goes on the grill.
Of course, use whatever marinade or brush you prefer. I'm just sharing what has worked well for me, and what I have received the best feedback about.
Wrapping fish is generally only needed when you're going to bury it in coals, and it acts to keep the fish clean and let it steam itself. Since you're not burying it in coals, I would lose the fig leaves and go by eye.
