Re: Twist Theme: Widening the Center column?
twist.css has a TABLE.maintext {WIDTH: 831px} specification, which apparently is what keeps things narrow there. You could try increasing that, but I imagine there could be subsequent adjustments to be made.
The author of Twist, gg, hasn't been around for quite a while so I assume he probably isn't interested in updating the theme. Because it's popular, though, if he doesn't step in, I wanted to update it for 1.10. At least the new features like fullscreen mode should be added. And since there will be tinkering anyway, it'd be good to make the theme more flexible size-wise.
About your menu question, Twist has its own mod-application_menu.tpl file, which may be incompatible with 1.10. You could try deleting or renaming templates/twist/modules/mod-application_menu.tpl, to use the default template, and see if that works. (Tiki uses a default set of template files for page layout, etc., but checks for any theme-specific versions. The theme-specific version will be used in place of the default, which gives flexibility to theme designs.)
-- Gary