Is there a way to get powerarmor training if you killed all the members in the bunker already?

If you do Arcade Gannon's side quest you can get power armor training at the end, along with a full suit of power armor (two if you play your cards right).

does he have to be a companion?

Yes

A word of warning - on the Xbox 360, at least, the quest is uncompletable, so you can't get the Power Armor training. A patch may have fixed this, but I'm not sure.

Yeah Arcade Gannon's quest is the only way you can get Power Armor Training outside of the BOS.

Maybe in Old World Blues we'll be able to get the ability to get Power Armor Training like Operation Anchorage.

Another option, though not very attractive, is to just use the NCR Power Armor, which doesn't require any special training. The stats aren't great, but IIRC the DT is a little better than combat armor. It's also immune to EMP damage, though I don't know of any enemies that actually use that against the Courier.

Um no i got it done.

You can get it done just as long its glitch free but its very glitchy.