Dear MamaKitty, hang in there. We'll get the old stitcher going!
I am no expert, but I have sometimes found that disassembling and cleaning and reassembling the upper tension can do wonders. Sometimes it is gunked up and therefore even though you are changing the dial, there is no effect.
Photos of the stitches you have sewn will also help; photograph both the upper and the lower stitches for us if you can.
:-)