I’m averaging about one per game too. Though I had this one round where a key ended up close to star and I kept getting more stars and collected EIGHT keys! It was amazing. I did 3 bronze chests and am now working on my silver. I like finishing the bronze last so it goes quick at the end (or as quick as it gets with one key a game)!
Finished it up and got Mal. She's okay at lvl 1, but I think she will do a lot more at lvl 3 or higher. (At L1, she clears two emoji from each corner, so it's not a terribly useful power for making boosts for racking up coins, and it does not charge quickly, in the couple games I have tried.)