Mark is correct. If you run a batch and it starts to run, it takes the most recent approved version of the email. If you change the email in the middle of the job, it does not care.
The way to handle broken items is to do at least one of the following:
- Abort the job with the abort button OR call support.
- Go into Images and fix the image
- Create a 301 redirect in Admin > Rules where you place the broken URL with the correct URL (you can still do this btw even though it went out)
As for the export limit, this is a built in limit in many situations. Ask support for help. I've downloaded much more but you have to restrict it to Visible Columns and then wait.