Awesome, Leo thank you so much! Both problems are fixed now!
I swear to God I will never touch that again; couldnt imagine how much you can mess things up.
Excellent. I'm glad that fixed it for you!
You can cause real problems by doing the wrong things to the directory, folder or EXE filetypes.
(If you mess up the EXE one in the right way then you can make it so you can't even run regedit.exe to fix things. 
I did that to myself a few years ago and had to think for a long time before I found a way out of that puzzle.)
From the changes you made, I think I can see what you were trying to do and what happened, and it wasn't you being stupid (don't worry!); you just did something that had unforeseen repercussions. Maybe we can make some changes to the filetype editor so it's more difficult to do the same thing, or at least shows some strong warnings before allowing changes to the Actions tabs on those filetypes.
Thank you very much for that reassurance, I really felt quite stupid after that happened. Also because I could not figure out why it would mess things up. I read the entries in the dialogues from how they had been and only shifted things - so I thought.
I would also welcome strongly some kind of warning or just make it a little more difficult to access the file types dialogue altogether especially for users who are more novice at this than I am (I kind of knew I could mess things up). On a sidenote, it is a big consolation to hear that even someone as knowledgeable as you, can get into a tight spot with changes made to the system. 
Anyway, you both helped me out of this thankfully; I think your support is really unparalleled.