Headscratchers / Street Fighter IV

• What exactly happens here?
  • The short version: In the absence of M. Bison the head of one of Shadaloo's weapon divisions, called Seth who is one of Bison's spare bodies makes a power grab in the organisation and creates a weapon system called BLECE. For this, and augmenting his Tandem Engine that makes him so powerful, he organises a tournament that will bring suitably strong fighters to him. It works too well: Chun-Li, Guile, Cammy and Abel destroy his facility, Ryu destroys the BLECE project and either Bison or Juri (Seth's right-hand woman) kills Seth, depending on who you ask. For smaller details that don't make sense (the precise events of the ending do take some unpicking), my advice is to search around a little online. Wikipedia is your friend.
• What was Balrog's ending about? He just randomly steals a kid.
  • My guess is that the kid will be a fighter in the next game where he will use PSYCHO BOXING!
  • In SSF4, he heavily implies that Bison plans to use the kid as a replacement body. It's also implied that the kid has special powers, and what looks vaguely like the Shadaloo logo briefly appears on his palm, so... yeah.
  • In SFV he is Ed the Psycho Power Boxer.