1- 8 pin if your motherbd has an 8 pin cpu connector or you can use two 4 pins.
2 - yes you can daisy chain the fans onto 1 molex. fans dont draw much power.
3 - one that can do ahci for SSD typically the first 4. Optical drive doesnt really matter but often a motherbd will have a pair of satas (5&6) that default to IDE/legacy.