I hate to be a debbie downer, and of course I know nothing about you, but from the information you've provided it looks like you are looking for a nice laid back side job to tide you over while you pursue your real interests. Based on that, I do not recommend you pursue a career in optometry.
To answer your other questions, I personally am very happy with my career choice. For me, it is absolutely worth it, and I would choose it again. For me. But I chose optometry for two main reasons: I believed it could provide a comfortable living for my family, and I had a genuine interest in the field. I have maintained that interest and have been fortunate enough to start my own business and practice the way I want, doing what I enjoy doing. I made it my career, and that has made it worth the price of my student loans.
However, I do not recommend optometry for anyone looking for a side job, or even for a nice backup in case they end up needing to work at some point. While there is the possibility of a flexible work/life balance in optometry, the most comfortable in the field are in private practice, particularly group practice. It very much depends on the job you get. If you are working for another doc, and they expect you to work x amount, you may have little to no control over your schedule, especially if you choose to work in an area where optometrists are a dime a dozen, which considering your interest in singing/acting, seems quite likely.
You will pay upwards of $250,000 for a job you'd rather not do full time, and if left doing full time may not enjoy. You might get the first job you land in a metropolitan area paying less than six figures (much less if you don't work full time) and begin to realize it wasn't worth the quarter million dollar loan you've saddled yourself with. That seems like a pretty high risk to take.
There is a common theme here where we see people who have not planned their careers well, assuming that putting in the time to get through OD school will guarantee a high paying job in their desired location, only to become completely disillusioned with the entire profession, crying that they were ripped off, and how no one told them about reality. Please don't become one of them, it really doesn't sound like optometry is right for you. There are easier ways to make a buck while you pursue your true interests.