Lets me see if I can answer some of these questions.
1. While it is frustrating, the fact of the matter is we are unable to control the actions of players leaving games. Its not really an issue so to speak, but we are doing what we can to monitor this type of activity and ensure that players complete games.
2. I am really not able to discuss exactly how the ranking system works. There are many factors that are taken into account when playing league play. Can you verify which one you are looking at your, your best rank, or your current rank?
3. Placement matches can take some time to properly reflect your proper rank. Have you played anymore matches besides the initial 5 in those leagues?
One of my Champions Series league teams has also been "Awaiting Placement" for about a week now and we played 10+ games. We eventually gave up because it never ranked us, which means we also can't compete in that league. Its definitely frustrating, especially since we did quite well and were expecting a high rank.
In order for you to get rid of the Awaiting Placement message, you got to keep playing games so the system can evaluate your actual rank, and put you into the most fitting division, or you'll just have to wait for a new sub-division to open. However, the last option is if you've played tons of games after the placement games, and still haven't been put into a division.
I noticed this aswell. I've played at least 100 games of league play in the past week and I'm still under the "awaiting placement" thing.
I'm not that bothered about getting a placement/ranking allocation as the main reason I play league play is that I'm sick and tired of the UAV spamming the most core games modes.
With respect to (1) - this is just a common occurrence. I understand that it is a tough problem for Treyarch to deal with, but as a player I have also found it INCREDIBLY frustrating. This has occurred to me way less now that I am out of Iron and into Bronze (and my suspicion is that it occurs even less as you move to higher divisions), but it is a serious problem for Iron players. My understanding, however, is that as you play league more this becomes less of an issue in later seasons, as your placement will take play from your past seasons into account, rather than simply your five placement games.
With respect to (2), as well as the related issues other posters mentioned, the time period about fits with the last week of league play (which we are currently in), and I've previously heard a rumor that you can't move divisions in the last week of league play. My experiences right now are consistent with this, as I am currently 1500 points up on the number two player on my Bronze ladder (with almost 9000 points!) and haven't moved divisions.
Although I've never heard anything about it previously, I suspect this also is causing (3). As a rough theory, if the ladders are locked in the last week, then that would mean not only that no one can move up divisions, but also that no one can be placed into any division, which would explain why teams have to await placement. My understanding is that when the ladders are not locked you are always placed into a division after five placement games, and my experiences are consistent with this.
Personally, I can understand why Treyarch locks the ladders in the last week, as it could be frustrating to be at the top of your ladder and have a player from a higher or lower division who has more points than you moved into your division (although I'm not sure anyone below Masters level worries about the rankings overly much, as they would always prefer to move up as compared to achieving a higher rank in their current division). I think if there was a bit more communication on the in-game interfaces about the end of the season and what it means that would resolve some of the questions people have.
Overall, though, I love the league play system and want to really applaud Treyarch for the job with it, although they'll probably never read my post. I think it's currently a frustrating system for Iron players (and Bronze players to a lesser extent), and the lack of transparency on moving up can increase this frustration, but overall I really enjoy league play. The other major frustration is playing against full teams who are obviously communicating when most players on your own team won't communicate (possibly because they are in a party), but this isn't a huge deal, and I suspect it gets to be way less of an issue as you move up divisions.
If I had any suggestion to improve league play, it would be banning parties as is done in SnD (both because SnD is played in league play and because it's annoying when your team mates can't hear your call outs). The other major suggestion would be to rework the divisions so you automatically promote players out of Iron who have played more than a set number of games without quitting, such as 30. If a player is playing this many games and not quitting, they deserve to get moved up to a league where they will at least consistently have team mates who aren't quitting, regardless of how good or bad the player is.