Greg if your photopost disk space is 2.5gb I doubt photopost is 4.3gb unless your housing other stuff there.
You can resize your thumbnails and medium size images under admin scan database.
As far as the main images you can not resize then without actually reuploading them on the edit screen and make sure your max image height and width are reasonable so your images are actually resized. If your max dimensions are large your main images could have never been resized but nothing I can say without more info.
Once you renew your access to support you can obtain support but right now your not entitled to support.