Harry,
I have to disagree that "...cancer will almost always originate on the surface of the tongue." Cancers start in the deeper layers and work their way to the surface. You should watch the video on the VELscope site and also read other links on the home page for a better understanding.
http://www.velscope.com/I wouldn't get a brush biopsy. The scalpel biopsy is the gold standard and the only way to really know if something is a squamous cell carcinoma. A biopsy does not require hacking away part of your tongue. A small area is removed, sutures are placed and it heals rather quickly. The stitches can be annoying and the whole thing can be uncomfortable for a few days. It's really no big deal.
Hope this helps you and you have to stop buying, using and then throwing away the "smokeless" tobacco.
Jerry