Try playing the tapes in a deck or another camcorder, then report back.
Borrow one from someone (you can use any home video DV camcorder to play them) or take the tapes to a professional production house (call them first) and see what they can tell you there after they
checks some of your tapes.
It does sound like you have problems with the camcorder heads,
But, I caution you to stop using the head cleaner at this point.
You could permanently damage the camcorder heads.
If it IS a head problem, you may need professional service help,