The screw driver helping the bobbin out has me really worried.
If the bobbin has been pulled out of round by prying it with the screwdriver, you are likely not going to get it to work correctly again. If the bobbin edges look wavy or bent, throw it away.
I am also worried about the ka-thunk sound.
Have you taken the bobbin case out and looked for bits of thread, lint build-up, etc.?
Use the manual, strip the bobbin area out empty and clean, clean, clean. Then Oil, if your machine has instructions for oiling.
Put in a new needle.
Wind a NEW bobbin, tightly (after threading for bobbin wind, I hold the thread lightly between finger and thumb to add a small amount of pressure and that helps the bobbin wind tightly.) I do not do this on all machines, just one which never winds tightly.
Rethread your machine . . . and, don't laugh, make sure your presser foot is down.
If it still messes up on you. Take it to a shop for repair or find another machine.
Good luck.