To the first question, yes, you can try to lower your cost on your on-board service, but beware of its rating as you don’t want to make it drop
you can also change your maintenance contract
or lower the salaries given to your employees, but I personally don’t recommend it, as it might effect your staff mood and lower the ratings of your flight
To the second question, you can try changing seats, pay your flight attendance more so their mood will increase, provide better on-board service.
Also, if you just can’t fill up your plane, might want to try interline with some other airlines to add connections to your flight