I was able to deduce the 2 digit grid entries and am pretty confident in some of the three digit ones, but my "logic problem" approach is failing as the grid entries get longer - a 6 digit grid entry has a clue answer somewhere between 317 and 999, which is too wide a range to narrow things down too much (knowing that a certain letter can have a value between, say 8 and 20 is not much help).
So my next tack to was set up the whole puzzle in a spreadsheet, so that entering 20 number/letter combinations will show the grid entries for all the clues. I think I have it down to about 5 or 6 letters that can take on any number of values, with the rest fixed or nearly so. Unfortunately there appear to be dozens of potential solutions (in the sense that the solution provides all the squared grid entries with the correct length). Most of these solutions are infeasible as they have 1A with a zero somewhere, which obviously can't work. None of the others I've come up with provide a 1A that will cross properly with the 1 thru 6 downs. So brute force is not working either.
Just as a check that I am not barking up the wrong tree entirely, are others finding 1a to be a negative number?
Must grade papers so I will try not to look at this for the rest of the day....fat chance....