At the moment, boorus and the other gallery downloaders are still on the old system, so when a file fails to import, it throws up those noisy error messages. When I switch them over to the new system, they will fail quietly, reporting their error text through the new url list window where you can retry them (if you haven't seen this yet, look for the new button icon on a thread watcher or a hard drive import page).
Hydrus's import file options are generic options for any kind of import, not specifically for boorus. They are tested after the file is downloaded, when it is passed to the database for importing. I didn't know you could do width:x in a booru query. Is there a way to say width>x (i.e. width is greater than x)?
Anyway, for now, if you want to filter before downloading, you will have to put your width:x height:x in the booru search box.