Multiple Photos/Assets in one upload entry
Forget about the front-end for a moment... That would be a separate, unrelated issue.

When you mass-upload, do all files appear on the back-end (screenshot #2)? And then when you hit "Save", are all of those assets saved?

If the answer to either of those questions is no, then you should file a bug report. Use the "Get Help" widget on your Dashboard, and be sure to include your logs, database export, and files.

If the answer to both of those questions is yes, then the problem is not with your file upload. The problem is somewhere in your template. In that case, please post a new question to ask why your template isn't showing all of your uploaded images.