python - Batch Converting ASCII into Feature Classes using shapefile lists

Problem. I have 413 ASCII files totalling 4 billion points, and my system cannot handle converting them to MULTIPOINT so that I can generate Terrains. Therefore I would like to create 12+ subsets of the area, using the lists generated from a shapefile(s).

1. 
   

   I've made my seperate Feature Classes listing the variable number of files that will make up each subset.

   
   
   


2. 
   

   I can generate (and print) a list of files from the Feature Class using the SearchCursor function.

   
   


3. 
   

   I'm running into problems using the generated list(s) to actually create the MULTIPOINT Feature Classes.

   
   

Here is my code:

# Import modules

import arcpy, os, sys, traceback
from arcpy import env


# generate a list of ascii files from the area-subset feature classes
env.workspace=r"F:\RTAMS\Petawawa\11-Library\LEGEO_Aug2012\LEGEO_Aug2012.gdb\LiDAR_ASCII"
fc=arcpy.ListFeatureClasses()

for fc in fc:
    cur=arcpy.SearchCursor (fc)


    for row in cur:
        fileName=row.TILENAME

        #this is the location of the ASCII files we want to import, so we change the workspace
        env.workspace=r"F:\RTAMS\Petawawa\11-Library\LEGEO_Aug2012\LiDAR\UTM18_WGS84\ASCII\FEATURES"

        # we should now have a list of files, which we will use to import into area-subset MULTIPOINT files
        # we set up some parameters for the ASCII3D to Feature Class tool


        try:
            arcpy.CheckOutExtension("3D")
            outWorkspace=r"F:\RTAMS\Petawawa\11-Library\LEGEO_Aug2012\LEGEO_Aug2012.gdb\LiDAR_ASCII_to_MULTIPOINT"
            inFormat="GENERATE"
            outFC=os.path.join(outWorkspace,fc+"_a")
            outType="MULTIPOINT"
            # find the ascii files listed in the search cursor
            txtList=arcpy.ListFiles(fileName)
            #Execute the ASCII3D_to_Feature_Class
            arcpy.ASCII3DToFeatureClass_3d(txtList,inFormat,outFC,outType)

            print outFC + " is complete."

        except arcpy.ExecuteError:
            print arcpy.GetMessages()

        except:
            # Get the traceback object
            tb = sys.exc_info()[2]
            tbinfo = traceback.format_tb(tb)[0]
            # Concatenate error information into message string

            pymsg = 'PYTHON ERRORS:\nTraceback info:\n{0}\nError Info:\n{1}'\
                .format(tbinfo, str(sys.exc_info()[1]))
            msgs = 'ArcPy ERRORS:\n {0}\n'.format(arcpy.GetMessages(2))
            # Return python error messages for script tool or Python Window
            arcpy.AddError(pymsg)
            arcpy.AddError(msgs)

Hoping you can help me out.