Did they use the gate macro thing, or did they have a ZPM? If they used the gate macro with a mid-point, would they suffocate in space?
The McKay/Carter Intergalactic Gate Bridge consisted of 34 gates placed at even intervals between the Milky Way galaxy and the Pegasus galaxy. When something was sent through the Earth gate it was dematerialized and sent onto the next gate's buffer, which in turn sent the dematerialized person or supplies onto the next gate without materializing. This was made possible by a macro written by McKay, which overrode the normal operation of the gates. The reason for this setup was because intergalactic distances were well outside the operational range of a normal gate.
The Midway Space Station was just the midway point on the bridge. It was useful as a security checkpoint in case the Earth or Atlantis gates were compromised, and was the only point on the 34 gate journey were something was materialized.
And yes, Carter became the commander of the Atlantis expedition in 2007 (Episode Reunion S04E03) and the Bridge was operational in 2006