Can't sync iPad due to 'over capacity' but it has 24GB free!

Hi all. I am no kinda power user of the iPad but I have been using this one successfully awhile and now am stumped. It's a 32GB Air. My son was using it, and when I took it over I changed accounts over, etc. I'm going to take it on a trip so I loaded up the Kindle app and was going to put some music on it...it had only two songs. Also I saw there was an update to the iOS too, so I did that. But now iTunes is telling me that it can't sync the iPad because it's 'over capacity,' by 14GB, with nearly 4000 songs on it. However that's not true, there are now NO songs on it, and the iPad itself shows less than 8GB in use. I have tried restoring the iPad to no avail. I also tried connecting the iPad to my MacBook rather than my MacPro, just in case that would help, but it didn't, in fact I couldn't get that to work at all, I never got the 'trust this computer?' message on the iPad.

And oh yeah, my second page of apps, including Kindle, has been stuck 'loading' for over an hour and doesn't seem to be working at all. GREAT.

Any suggestions welcome! But I've only got a couple of hours to solve this before my trip.