1 - To fix the target of target picture bug :
As I said, the extended target of target panel code has to be accompanied by an updated (enlarged) picture in order to fit to its new size.
the picture name is target_vitals_backdrop_mini.tga
it is included in this minimal theme https://www.lotrointerface.com/downloads/info598
Put this picture in the same folder than your skindefinition.xml file.
Now in your skindefinition.xml file you will have to add (or edit if it already exists) this line
<Mapping ArtAssetID="target_vitals_backdrop_mini" FileName="target_vitals_backdrop_mini.tga" />
2 - Sorry I did not understood what you meant when you said "Portrait -> health/man bars -> Portrait -> 1/2 size health/mana bars"
3 - Yes, skinning allows to create a target of target panel frame as big as you want, but it takes time and it is a boring process.
4 - The custom toolbar themes.
Only theme variations including "custom" in their name require to edit the skindefinition.xml file to position the main toolbar a the bottom center of your screen depending your graphic resolution. There are only 2 values to edit : X and Y inside one line. But when combining it with a zoom in ui settings I don't know how it has to be managed.
However, you can have a look to these skins without having to edit the skindefinition.xml file, the toolbar will just not be located at the right place but you can see how it looks (don't forget to log off your character after selecting a custom toolbar theme in order to load the new panel settings on the next log in of your character).
The same panel modifications that are included in "Extended and enhanced panels
" are also included in "JRR Skins Collection
" and "JRR Azure Glass