With the exception of part#4 of your question, it basicly boils down to the same suggestion as this node, except that was regarding all links on PM, and you are only refering to the Chatterbox. All you would need to do is set up your Custom CSS to show links to your home node in red (or wahtever color you want)

And as long as I'm linking to that thread, I might as well link straight to Aristotle's Comment, which points out that browsers supporting "CSS Level 2" can do this without any changes to the HTML generated by the site.