Hello there, oder soll Ich auch Gutten Abend sagen?
1.- About the skins, some of them come on DAT files, and others simply TGA fles.
The best option you have is to enable them, no matter if they are TGA or DAT via JSGME (It'a very cool program that makes a backup or your files, so, when you want you can disable a mod and the files are restored) check the link
http://www.users.on.net/~jscones/software/. It's very simple and easy to use, but it is also a very powerful tool that spares you a lot of work.
2.- About using Mini Tweaker, when you change something with this mgnificent progar (I use it myself very often) itcreates a copy file in the same directory, and if you do not delete it, SH3 will keep reading the copy file (original) and not the one with your modifications. You must delete the copy file file or move it to another folder in case you want to restore it later. This proces must be done everytime you use the Mini Tweaker program. If you see that strange number, like scientific notation, you should better reinstall SH3 from scratch to avoid future problems. If I am not mistaken that kind of values is a sign that something is wrong.
Hope this info was helpful, even if I am not certain if this is exactly what you were asking.
Anyway, if you have other questions or need further help, just let me konw an I wil be more than happy to help you if I can.
CapZap