Should I retire my scratched non-stick rice cooker?
There is no way to salvage it, no. The Teflon will stay scratched and flake into your food. Even after you remove the large flakes, it will continue shedding microscopic ones. 

We cannot tell you anything about "should" or make decisions for you. If the risk of eating Teflon is acceptable to you, keep it. If it isn't, throw it out. Discussions on the long-term health effects of consuming Teflon in tiny amounts fall into the "is it healthy" category, which is unanswerable for us. As always, there are the people who say it's terrible, and the ones who say it's no big deal. You have to find other sources and decide whether you want to believe them.