As it is now, you can't challenge someone if they are already involved in another challenge. You can only challenge up, so if everyone above you who is within challenge range is in a challenge, you have to wait. No way around that.
Your position on the ladder is not based on Kills, Deaths or K/d. It's based on you beating someone above you. If you win you move up. That is the only way to move up the ladder. That's the main reason there are penalties for non-Active players and players that repeatedly decline challenges.