At that rate with a cxp cap of 1.23 million for Command Rank 300 you would have to run your favorite chapter(s) 6,150 times to reach the cap lol. This is assuming that you run the chapters on a day where they are not the bonus and giving only 200 cxp per run. If they are the bonus you get 240 cxp per run so it would drop to 5,125 to run chapters for cxp.
Welcome to the grind. Have fun!