I haven't check to see which all files would need to be edited but here is the code for libraryfiles.html that will give you a tool tip.
libraryfiles.html is the template used for images and videos.
You only get the tooltip when hovering over the thumb not the text.
I bolded the changes.
<!-- begin: if([CurrentLibraryItem.UseThumbnails]) -->
<!-- begin: loop(z, [Pagination.StartIndex], min([Pagination.FinishIndex], [LibraryFilesCount] - 1)) -->
<div class="thumbitemcontainer" >
<div class="thumbitem" >
<!-- begin: if([Mode.IsRemote]) -->
<a href="javascript:download_jump_playing_now('MCWS/v1/Browse/Files?ID=[CurrentLibraryItem.ID]&Action=Play&Zone=[ModeZone.ID]&ActiveFile=[LibraryFile([z]).FileKey]&Token=[Token]')"><img src="[LibraryFile([z]).ImageLink]&Width=136&Height=136&Pad=1&Format=png" class="thumbitem" title="[LibraryFile([z]).Name]" alt="[LibraryFile([z]).Name] Image" />[/url]
<div class="title">
<a href="javascript:download_jump_playing_now('MCWS/v1/Browse/Files?ID=[CurrentLibraryItem.ID]&Action=Play&Zone=[ModeZone.ID]&ActiveFile=[LibraryFile([z]).FileKey]&Token=[Token]')">[LibraryFile([z]).Name][/url]
</div>
<!-- else -->
<a href="[LibraryFile([z]).WebPlayPlayLink]"><img src="[LibraryFile([z]).ImageLink]&Width=136&Height=136&Pad=1&Format=png" class="thumbitem" title="[LibraryFile([z]).Name]" alt="[LibraryFile([z]).Name] Image" />[/url]
<div class="title">
<a href="[LibraryFile([z]).WebPlayPlayLink]">[LibraryFile([z]).Name][/url]
</div>
<!-- end: if -->
</div>
</div>
<!-- end: loop -->
Edit: will look into breadcrumbs, time permitting as I have never used them before.
To prevent updates from overwriting the changes make a copy of the default folder and rename then set the appearance option for webgizmo to the new folder.