Since your server is 6.3.5, you are running a very old version of CA which is using an outdated and unreliable application feed that doesn't even have 1/10th of the apps available. CA has required 6.4+ for quite a while now and the URLs for the feed changed a long time ago. Update your server and CA
It only scans when opening that page if no scan has yet completed. Scans run 10 minutes after start of the array and also on whatever schedule you may or may not choose.
After 120 seconds if it doesn't complete, it never will. Reload the page, and if it doesn't bring that back up, then it's done. It's on the todo list to change how that popup works
The way it seems to me is that your version of firefox isn't rendering anything correctly. The only way you should be able to see 6 columns when you're on at maximum 1920px across is either setting the zoom of the browser very small or setting the dynamix font size to be very small AND a zoom level very small
In your case, it appears that the font-size is relatively a normal size and the zoom is more or less normal, but your browser is deciding to ignore the box sizes I've specified which it does not do on a Windows platform (nor any other browser I can throw at it or Safari on a Mac, or my phones / tablet's browsers)
I could make up something long, convoluted, and technical as a reason why it doesn't do that but it would all be bs. The simple answer is that when I did this, I never thought of that, and why it still doesn't do it is pure laziness
VM's vdisks are stored by default (can be changed) in the domains share. Which is default use Cache:Prefer. So yes it would stay on the cache drive.
When clicking into a share from the Shares tab, click on Help (or the ? depending on unRaid version) and you'll see the options explained.