This could be due to a permissions issue.
Ask your intern to copy the files onto her computer's desktop and to try opening the gallery from there.
Once the gallery has been edited, the files can be copied back onto the flash drive.

To initially hide the thumbnails in Large Screen Mode, set showThumbsOnLoad="FALSE".
To hide the 'Toggle Thumbnails' button (to prevent users from toggling the thumbnails on and off) set showThumbsButton="FALSE".

If you want to get the thumbURL of the image currently being displayed, you can use the Juicebox-Pro API methods getimageIndex() and getImageInfo() in conjuction with the onImageChange() event. You could then use JavaScript to determine more information about the thumbnail image, such as its dimensions.
For example:

<!--START JUICEBOX EMBED-->
<script src="jbcore/juicebox.js"></script>
<script>
    jb = new juicebox({
        containerId : 'juicebox-container'
    });
    jb.onImageChange = function(e) {
        var index = jb.getImageIndex();
        var info = jb.getImageInfo(index);
        var thumb = info.thumbURL;
        
        var img = new Image();
        img.src = thumb;
        var w = img.width;
        var h = img.height;
        alert("Current thumbnail dimensions: " + w + "px x " + h + "px");
    }
</script>
<div id="juicebox-container"></div>
<!--END JUICEBOX EMBED-->

The thumbnail page is displayed in Small Screen Mode only (and not in Large Screen Mode).
You can initially hide the thumbnail page in Small Screen Mode by setting showSmallThumbsOnLoad="FALSE".
You can also prevent users from accessing the thumbnail page by setting showSmallThumbsButton="FALSE".

You can force a particular screen mode to be used on all devices and in all browsers via the screenMode configuration option.

Also, you can disable the Splash Page by setting showSplashPage="NEVER".

Hopefully, with a combination of the above options, you will be able to have your gallery function as required.

For reference, a full list of configuration options can be found here.
For more information about screen modes, please see here.

Add SEO Content is not a configuration option that can be added to a gallery's XML file.
It is a feature only of JuiceboxBuilder-Pro and the SEO code is generated at the time the gallery is created (not when the gallery is displayed).
You would need to manually embed your Juicebox-Pro gallery in your WordPress post (using the baseUrl method of embedding) and copy and paste the SEO content (generated by JuiceboxBuilder-Pro) along with the embedding code into the body of your WordPress post (ensuring that the method of entry is 'Text' rather than 'Visual).

This bug has now been fixed in v1.3.2. Please see the Version History for a full list of changes and the Upgrading Juicebox page for details on how to get the latest version.

The bug I referred to in my first post in this thread has now been fixed in v1.3.2. Please see the Version History for a full list of changes and the Upgrading Juicebox page for details on how to get the latest version.

The expanding multiple galleries bug has now been fixed in v1.3.2. Please see the Version History for a full list of changes and the Upgrading Juicebox page for details on how to get the latest version.

This bug has now been fixed in v1.3.2. Please see the Version History for a full list of changes and the Upgrading Juicebox page for details on how to get the latest version.

In order to install a new version of JuiceboxBuilder-Pro, you must first uninstall any previous version via the Control Panel.
Also, please see the Installation Issues section of the JuiceboxBuilder User Guide which may help.
If you continue to experience difficulties, please let me know how far you get into the installation process and what errors messages (if any) are displayed.

Thank you for reporting.
I have notified the developers.

Do you have a sample gallery that I can take a look at which shows this? Also, what device(s) and browser(s) do you see this in? (In my own test gallery, the icons are the same height as each other.) Thank you.

When the 'Add SEO Content' checkbox is selected (in JuiceboxBuilder-Pro's 'Customize -> Sharing' section), the SEO code generated already includes 'alt' attributes in the <img> tags, populated by the image's caption.

This is not possible. Juicebox requires that the image data be stored in an external XML file (the location of which is determined by the configUrl embedding code option).
The only alternative to not using an XML file would be to use a Flickr account as the source of images.
You could set your Flickr configuration options in your gallery's embedding code (on the HTML page).
There would still need to be an XML file present but it could simply be a dummy file with just a <juiceboxgallery /> tag as no data would be used from it.