By the time I am posting this reply you may have already developed your tool with keyword driven testing for Mobile Applications. If so, I would love to learn about it from you, if you still haven't done it yet, the below answers maybe useful to you.
Since you mentioned trying to automate Android Applications, a good alternative for appium could be Espresso and Robotium which are the other open source tools that are widely used and have a lot of support online. One reason people go with Appium is you can have the same code base that would work for both iOS and Android. You wont get this flexibility with Espresso or Robotium.
This is something to think about if in the future your company decides to do iOS app implementation as well.
For you other question. Robotium is pretty much like Selenium for Android app testing. It has very similar features. Read this article for more info - https://www.360logica.com/blog/robotium-selenium-android/
Hopefully this gives you some idea about the differences and similarities.