When I add Witching Gadgets to my ModPack I can no longer open any World or close my MC instance. It gives me this Error while trying to start a world:

Also if that's helpful, my modcount in MC adds +2 for WitchingGadgets instead of +1 or is it more then on mod in the *.jar?

Yes, WG contains a coremod, that's why it shows +2. That image you showed is a generic error message. I'll need to see the whole log (on pastebin or similar) to help you.

http://pastebin.com/DgMU9LgE

go into the config, disable transmutations.