Getting the logo top-left is going to be big for any stand-alone community but if we can embed the forum into a website for many it won't matter as much. But still, the core audience wants that top-left logo no doubt.
Notifications didn't work the other day here either and seemed fine now.. a second good luck to @Julian in tracking that gremlin down
2 I agree but I think one of the issues is what width you view at. You're screenshot is showing easily double the empty space there. I'm using 1/2 a 27" monitors width for my web browsing right now and it's easily 2" less room there. I almost wonder if going 2 lines deep would help (and give that extra height for larger logos) provide enough space from a responsive standpoint to fit it all in.
4 Agree 100% -- The log out can drop down off the user name (maybe with the users link under it as well) and free up a ton of space in the middle. Maybe then on my narrower web view those social / donation / etc.. icons have the space needed..