Sub domains do not give a ranking boost. While I was a subscriber at SEObook, Aaron Wall put it like this:
creditcards.com = boost
creditcards.example.com = crap
cardscredit.com = crap
Don't worry about KW in the domain. If you can't rank any other way than to rely on the KW being in your domain, you don't deserve to rank. If I were your competitor, then all I would need to do is get some real FB URL Likes and a couple okay external links.
If you are going to 301, make sure you have your .htaccess ready to go ahead of time. Also re-submit your old sitemap in GWT 1st so it crawls your site and notices the 301s. Then submit your new sitemap.