Dragonair Decision

You are going to regret big time if you evolve the lesser CP Dragonair as you, for the needed candies to get it up to a decent level would be halfway to another Dragonite. I'm estimating your high CP Dragonair will become a ~2450 Dragonite and that is going to be usable right away in Gyms, but the other will be more like ~1000, completely worthless. IVs make a really small difference all-in-all, and remember you are probably not going up against perfect IV pokemon in most cases.
Shortly: CP makes a way larger difference here, evolve the high CP one. 6 IV points difference is not worth ~75 Dratini candies

Yes, definitely the one with higher CP. It's going to be a decent dragonite in any case, regardless of the moveset (if you get a bad moveset, just start sparing candies for new dragonite). The IV difference is so small it is practically meaningless in this case.

Save the candys and wait for a 90%+ IV to come by, if you really pretend to play this game for a while, trust me, you are gonna end up catching something better till you reach level 32, 33 (when leveling up starts to be really hard); that's only what I would do and not what you really have to do.

General rule of thumb the higher CP one is better (of course depends on moveset, but you dont know that now, plus dratini candy is too rare), unless its a perfect pokemon, then you might want to keep it for the future