1. ...Booster Draft?...
There really isn't a very effective way to use Doubt unless you're running an orange defense and put it in there just for the fun of it. I guess one kinda fun thing you can do with it is just leave it your territory even after the turn has expired and he's no longer an EC (since it says, "Place in a territory. When played,..." you can just leave it there). Then later you attack with Nathan to shuffle it back into your deck and use it again. I've never tried but it'd be cool just to say you used a dominant more once in a game.
2. I'd say use a mixture of both. Depending on what your opponent is playing either will come in handy during certain situations. I guess it mostly depends on what cards you're play (for instance, I wouldn't suggest including Ira in a Genesis deck just because he fits the brigade, however I probably would use Benaiah in a prophets deck so it really depends on the offense/defense). Typically, I think that low-numbered characters are better for those powerful enhancements but I usually include at least 1 FBtN character in my T1 decks if not more. They typically end up being The Strong Angel, Moses, and Captain of the Host. Defense I'd say definitely the low-numbered guys more just because of all the CBN good enhancements running around. The only FBtN ECs I would really consider using now are KoT and Sapphira on occasion.
3. Typically you just don't. Unless they have some cool, useful ability (The Strong Angel, Michael, Saph, Goliath) then I'd say they're probably not worth it. If you were to use them though, I'd say make sure you include some interrupts and negates so that when your opponent does get to play first you've got some ammo to return fire in case you get the chance.
4. When you say "David" I'm not really sure if you mean purple kings or red warriors as those are both fairly common. For a Revelation theme I guess there's really not good way to combine the defensive cards as there really aren't all that many good ones. For offense silver is pretty good but it'd not all-encompassing. I guess you could try black and pale green and use: Wrath of Satan, Locust from the Pit, Death and Hades, Beast from the Sea, Frog Demons, Wings of Calamity, Satan Released (works well with High Places), Ancient Evil, and Torment. Those are really the best evil cards in Revelation along with the always splash-able Red Dragon. I suppose if you use Red Dragon you could also use Habitation of Demons, Number of the Beast, and if you're super desperate, Whore of Babylon and Babylon the Great but you'd be stretched out pretty wide there.
Hope this helps!
