My Corny Keg Priming Sugar Ratio is Off, Now What?

Okay, I think to answer my questions I should give a quick background..

I just finished fermenting a 5gal batch of porter. My plan was to bottle half and keg the other half. I was going to siphon half into the bucket with the priming sugar (half the normal 1 1/4 cup, or 5/8 cup extra light dried malt extract) and bottle that. The other half was going into the Corny keg; I usually force carbonation for 3 days at 30lbs.

Where I screwed up: When I was siphoning into the priming bucket I accidentally siphoned the whole 5 gallons. So I had the full batch with half the proper amount of priming sugar. But thinking about it, I wasn't too far off from the ratio suggested for conditioning in the keg with the ratio of 5 gal > 5/8 cup extra light malt extract. This wouldn't be too terribly far off from 1/3 cup corn sugar since you would double the amount when using malt extract. So in the end the keg has 5/8 cup vs. the usual 2/3 cup dried malt extract.

So what I'm wondering is: do I continue to condition the beer 1-2 weeks like this? I've never conditioned beer in the keg, I usually force carbonation. Since the keg is only half full, is the air in the sealed keg a problem? Should I hook it up to CO2 and pressurize at dispensing pressure while it conditions?

Thanks for your time reading this and your suggestions!!

I'd hookup the CO2 and purge the keg. Pressurize to 15 psi & vent. Do that 3 times & you'll have most of the air/oxygen out. Then leave it to carbonate. You can force it later if necessary.

Yes and make sure to let it condition in bottle-like temps.

The good thing about the keg is even after you tap-to-serve, you can adjust the carbonation levels by degassing or increasing the PSI.

Thanks guys, good info.