Even with the scale option on the top left of the addon RFS looks like this to me:

Would it be possible to resize the addon window? The main issue I have at the moment is with seeing the list of spells in things like the Blacklist.

That's what the "Hide Settings" option is for, I'll think about adding a resize option, I like the fixed size more since the content of most tabs doesn't scale well. Maybe I will add a button to open the list in a separate scalable window.