I wouldn't say you done anything wrong. I'd say its the forum not being forgiving if you want to remove an album.
If you find 350 photos per album isn't enough just let me know. you till may want to limit yourself to uploading 100 at a time, you can keep adding to the album up to 350. But what I find is uploading more than 80 photos, each photo there after seems to have a larger and larger gap between each image upload.
It would be nice to set up 350 images and leave it going, but I believe it times out in the end.