You were half right.
From the ODBC documentaion:

DecimalDigits. The number of decimal digits of the column on the data source. If the number of decimal digits cannot be determined or is not applicable, the driver returns 0.

Nullable. Indicates whether the column allows null values.

Primary key information would be at least as useful to me as decimal digits. I'm guessing that decimal digits are the second argument to the number(,) datatype? In fact because of this, It doesn't seem like I'm going to be able to fully automate this process.

After over an hour of looking through ODBC and Access Documentation I still can't figure out exactly what datatypes map to which integers in the second column. It's maddening. I'm still working on a solution to this.