I cannot give more answer. But at a quick search i found
this post from erel saying that the dir.assets have no subfolders.
So i would think the files are ALL in Assetsfolders root or even are not copied due to that they are NOT in the Files-Folder of your Project directly.
To Q1: The files are copied completely to the Asset (with subfolders). You can NOT access subfolders in DirAssets so you should copy all files to projectdir/Files/ without Subfolders.
What i tried. I put a copy of a folder medicoicons\ with some images insige to projectfoldder\Files\medicoicons\ (and here some images)
with
Dim flist As List
flist = File.ListFiles(File.DirAssets)
For i = 0 To flist.Size - 1
Log(flist.Get(i))
Next
I got
images
medicoicons
sounds
webkit
So i tried to look inside the folder medicoicons
Dim flist As List
flist = File.ListFiles(File.DirAssets&"medicoicons\")
For i = 0 To flist.Size - 1
Log(flist.Get(i))
Next
i have tried File.ListFiles(File.DirAssets&"medicoicons\") in some combinations. With \ at beginning, mit / at beginning. with \
With no luck. But maybe i´m doing it wrong (i´m beginner)
To Q3: I´m not sure but i think -IN A WEBVIEW - they are both possible. The second more than the first one.