1. In normals, you're matched up with players who are around your (hidden) normal elo and around the same number of games. In ranked, you're matched up with players who are new to ranked and around your current elo. It's possible that your normal elo is higher, so your ranked elo will catch up to it over time.
2. People have asked Riot to declare pick order or call order as the rule, and Riot has consistently responded that the only rule they will support is "Don't be a jerk." If two people on the team want the same role, the whole team benefits if they reach an agreement instead of arbitrarily handing the role to one of them and forcing the other into an undesired role.
3 and 4. Your teammates and your opponents should disconnect with approximately equal frequency, so your elo remains accurate even if you occasionally have to play a 4v5. A game can end with a result of "Loss Forgiven" if there is major disruption in service resulting in mass disconnects or unplayable lag. This is not done for individual disconnects, so there is no procedure for requesting it. Allowing players to regain lost elo for bad games could lead to a lot of problems. For one thing, the average elo would increase over time, unless you also reduced elo for the winners of bad games. Also, it could lead to a situation where players would gang up on a teammate, blame them for the loss, and bully them into disconnecting in order to invalidate the game and avoid a loss of elo.