have been at a festival all weekend and had no time to look at this, but now I am playing...I have a number of graphics programs, but the one which looks like it will really help is "Paint Shop Pro"...it is one step below Adobe PhotoShop, but will do almost anything you & I are likely to need...a lot of it automatically...I saved one page from the site and loaded it in PSP, and found a menu of 'filters' which will enhance graphics in several modes...it really seemed to make a difference...
the program I have is a 16 bit shareware version which is probably a couple of years old...they have even newer versions now that are quite sophisticated..I am trying this for awhile till I can afford to invest...(it does not 'expire' in this version...it is, I think, intended to whet your appetite for the fancy version...)
anyway...I think that it might allow enough enhancement to let us read the trickier of the scans...