Another 2 get taken for eating/commuting if you live close to work, let's say you spend another 1-2 per day taking care of your school-aged children, so now you're down to 20-30 hours a week. Let's say you spend another 5 of those doing social things, that's 15-25 hours a week. Subtract another 5 to deal with errands... 10-20. Some more of that will likely go towards your spouse.
That means you get something closer to 500-1000 hours a year. Perhaps you can get more if you carefully prune.
That's enough to do stuff, not enough to accomplish a second career.
And after you finish all of that you absolutely want to spend those last few hours sitting down and resting. You will quickly burn out if you spend every minute busy.
Unless the work is a rest time. Not every job is demanding and if one turns of emotional reactions to workday situations then one will have more energy for later activities.
it's not only that - everything else will be competing for those 10-20 hours (e.g.: gigs for extra money, learning, teaching, life-administrativia, personal growth, burnout, ...).
Put another way, your life might be complicated, but more improvement does require digging a bit deeper than the status quo, so it's still up to you to find or make time/energy to work on things.
I'm in no place to tell you how much time or how to manage it, but you do get out of your time what you put in, and there isn't a shortcut for that.
I have school aged and younger children and recently came to the realization that I am not willing to sacrifice time with them or my spouse for side projects, so I am content with the 4-8 hours a week I have to myself to work on projects until they are a bit older.
That means you get something closer to 500-1000 hours a year. Perhaps you can get more if you carefully prune.
That's enough to do stuff, not enough to accomplish a second career.