If my memory serves the large screw that's attached to the counterweight is threaded right handed. In other words, it loosens the opposite way normal screws loosen.
You'll need to get rid of all of the rust in the bobbin area. I had a Singer 15 rusted solid and it was the hook area that stopped everything from moving. A few days with WD-40 and the machine started to move. Lots of rust and gummed up oil throughout. After lots of hours cleaning rust I now have a machine that sews perfectly. I suspect yours will clean up fine too.
Last edited by 1.41; 12-02-2023 at 03:05 AM.