Step 1: Look at unsold goods. Bulldoze commercial of appropriate wealth levels until unsold goods are close to 0. Now those commercials will be taking in the right number of workers for the goods required. I expect this will free up ~2000 workers in your case.

Step 2: Bulldoze high density industrial... constrain it to medium density. You don't need super dense empty factories. I expect this will free up 3000-5000 workers in your case.

Step 3: Service buildings. Consolidate police and fire into fewer larger buildings. Each building requires workers while the extensions do not require any more workers. Check the number of workers at a service building by pausing the game, checking the city worker count, powering off the building, comparing the new worker count (you can power on the building at this point if you want to keep it). In particular, things like CoalMines and other specialization buildings require a lot of workers. Limit the number of these that you have.

Step 4: Residential density. If it's not all high density yet, you have room to grow. If you're having trouble balancing the traffic of low wealth residential, make a community college or university to upgrade your industrial and focus on medium wealth residential.