I can't be certain when that area figure was derived, but the area covered by Sutton Heath (part of the married quarters, as you say) is a pretty small proportion of the whole base. I'm not sure if the Army retained any of the married quarters - and if they didn't, where they put families now. There were quite a few MQs at RAF Bawdsey Manor, but I think they've all gone now. Of course, there were bucketloads at Bentwaters, maybe they still have some? (Bentwaters itself is a much bigger camp than Woodbridge and had size been the issue, would have been a much better choice). The new-build barracks are on the site of what was a fairly ramshackle group of engineering buildings. They reclad and reconditioned many of the USAF buildings associated with the airfield, and they destroyed the rather splendid Officers Club to make a new combined Mess, sadly.
I think the runway at Woodbridge is technically under 'care and maintenance', but the Army have never paid more than lip service to that categorisation, and have made unusable pretty much every ex-RAF airfield they've taken over (which is a huge number). It's a shame, because it's one of the three emergency airfields built in WW2 which had runways of 9000' by 750', especially to be able to accept lots of crippled bombers on their way home. The others were Manston and Carnaby.