Please ask one question at a time, since I'm not sure which file to open to analyze which issue.
I'm looking at the issue where you reported default file names not being used. You should be able to do it the way you want and shouldn't need separate pages.
In the file boat_insert_images.php you don't have default files specified. They all have:
'DefaultFileName' => "",
I don't really fully understand the second question. Can you include a screenshot of the page you are asking about? It sounds like the label is wrong and it should say "Choose the event to trigger the file upload"
The file field should be the name of the <input type="file"> field from your form. That is how the uploaded file is specified.
Did this help? Tips are appreciated...
