It's most likely a small formatting error (very likely resources) that the game ignores - Geomod is a bit more rigid.
Make a back up of the descr_strat file and then first check if the top has a faction list that contains these elements:
Most mods do not have the unlockable end set - Geomod requires it. Simply add it between end and nonplayable.
If that is not the problem then delete the complete resources listing, entries look like this:
This usually takes care of most 79% freezes.
resource coal, 24, 179
resource tobacco, 16, 179
One suggestion - do not use Geomod in your original mod, if there is another error and you save it might totally scramble your original files. The safest way is to install my Bare Geomod set up and then copy over all text files in the data folder, the text and the (complete) world folder.
Once you have successfully change your forest and saved you can simply copy the map_ground_types files to Rusischi and delete the map.rwm there to force your new map to be generated.