Marching band is a challenge with a family and children but I know a lot of folks that have been able to make it work. If you don't want extra hours at work, look at teaching middle school or Elementary music. Limit after school to only the things that must be (do you really need sectionals 5 days a week during concert season). There are things in this career that you must do outside of the school day but...

You will probably spend more time at work than at home. If you had a normal 8 to 5 job in an office you would spend more time at work than at home (awake). Small business owners sometimes have it worse. The trade-off for teachers is the time at home during the summer or the many breaks like Thanksgiving, Christmas, and Spring break to make up some of that lost time. My spouse at a previous job was gone from 6:30 to 6:00 not as a teacher including commute. Unless you find a work-from-home gig (which if you listen to a number of business reports are getting fewer and fewer as folks go back to the office), expect to work for a living.

Your job becoming your personality is for you to decide. Some folks find their identity in their work. Others find it in their hobbies. Others find it in being a parent or grand parent and the legacy they leave behind. I wouldn't say that is not normal. Might just not be for you.

Work life balance is a word that gets thrown around but isn't reality unless you the entire US economy moves to a 30 hour work week which isn't going to happen in my opinion. 24 hours in a day. 8 hours of work, 1 hour of lunch, 1.5 hours in commuting, 7 hours of sleeping, and you have 6.5 hours before or after work where you are awake and doing something else...