Support Forum

For the first question - easiest to look at the FAQ for more detail: http://codex.simple-press.com/.....her-tools/

On the second then this is constrained by your Wp theme so you need to allow for more space on the template you are using for the forum page. For example - if you arr displaying a sidebar perhaps you could remove that.

This is still a product of your WP theme where it will have defined the container to a fixed width. We cant really produce worthwhile documentation because every Wp theme is different.
If you give me a link to your site then I can take a look as you can find out with tools like firebug very easily.