1. a 10 gallon for a small group of samurai gouramis plus rasbora is pushing it, imo. they should at least need at 20 gallons minimum for a group plus the rasbora.
2. if you're wanting to breed licorice gourami, then you're going to have keep them in a species only tank if you want to be successful in breeding. not only that, but they're endangered due to habitat destruction so it's important for hobbyists to at least attempt to breed them
3 betta imbellis is the best choice imo. they're not endangered or require a large aquarium. however, if you're going to keep them with rasboras, it's best to get one. if you get a pair, they may breed, and the male will defend the nest by chasing away any fish that may get too close to the nest.