Are you allowed to have two different official transcripts on your erb for promotion points?

This happens quite often, and yes you can. The trick is to sort out if any or all credits transfer from one school to the next, as you can't get the same points twice. That is for the admin folks to figure out, but a letter from you can help with that.

Is your civilian education maxed out with just one of the transcripts (regardless of whether you graduated from there)? If so that should be all you need. If not then yes. Any transcripts from an accredited college or university that ups your civilian education point total is fair game.