Ah, then the solution is probably even simpler! When adding a new install location, you need to click on it to make it the default: your preferences tab should look like this:
I'm making a note to make the UI clearer!
And patching.. yes, I was hoping for this. It's kind of a drab to redownload AC fully every week with a 16 MBit/s line ;-)
Oh yeah, it's been annoying me as well! As a motivation, I promised myself I wouldn't play anymore AC until that's fixed :)
Thanks for your patience!