You haven't told us anything about what you've done to educate the staff about writing up defects. Have you done anything? Unless they also work as technical QAs, they almost certainly have no idea what is expected in a defect report.
I'm surprised that the primary problem doesn't have to do with listing ambiguous steps to reproduce a defect. For example, "I went to the page again" vs "I clicked the link again" vs "I closed the browser, reopened it, entered the URL, and then clicked the link on the page again."
Of the 3 things you mentioned (#1: screenshots of the YSOD that don't include the page URL, #2: scaled screenshots that are unreadable, #3: the complaint that wants to be a bug report but is still just a complaint), the first two sound like *you* are complaining -- if they're not technical people and they don't know how your system works or what you need to see in order to diagnose a problem, then the first two issues should have been expected.
How do you solve #1 and #2? If you're asking users to perform rudimentary QA, you're going to have to work with them. So, the solution to the first two problems is for you to realize you need to help out in these situations, explain what was wrong and what they can do to fix it next time. They don't know what you need in advance. Progress will be incremental but sure. And if they have to do all this in addition to their other tasks, then be nice while you're doing it.
How do you solve #3? First, if people are complaining then make sure you're not overreacting to a real usability issue and ignoring it because it's not in the format you wanted. Then mail a template with a description field, a steps to reproduce field, an expected results field, and an actual results field, with a description of what each one is. Have a meeting explaining how to use it. Give examples, especially highlighting the need for detailed and unambiguous steps to reproduce.
As bad as e-mail is for tracking issues, if this is a short term thing it may be the best approach. If you can see this going on, getting away from e-mail is a very good idea. Having recently been through a issue tracking system transition, getting everyone used to the new systems took some time even though it was handled very well (and not by me).