I can try to help but I'll need a clear set of pics of the front, top and back of the machine. Especially the controls.
But first I'd suggest popping the top off and oiling anything that remotely looks like it should move, then gently turn and move every control while you watch what it does.
I still don't have a manual for my Alden machine and that's pretty much how I figured out how it works.
If the old Singer treadle is fixable I'll try to help on that if I can. I'm a sentimental old fuddy duddy and family artifacts mean a lot to me.
Joe