Split a grid into a grid
Pyth, 30 29 26 24 23 bytes
sm.Asmmq1ssbCkds./MC./M

Try it online.
I'm sure this will get shorter. This is O(2mn), where m and n are the width and height of the array, but completes the last two test cases in 45 seconds on my laptop on battery (i5-5200U with limited performance).
Outputs the number of solutions.
Explanation
Five-dimensional arrays are really fun to work with.&lt;/sarcasm&gt; You are not supposed to understand how this works even with the explanation.
                    ./M    Find all partitions of each row. Now we have a list of rows,
                           each containing the ways to split the row, each containing
                           the parts of the split (3D).
                   C       Transpose. Now we have a list of ways to split the columns,
                           each containing the rows, each containing the parts of the
                           row (3D).
                ./M        Find all partitions of each row list. Now we have a list of
                           ways to split the columns, each containing the ways to split
                           the rows, each containing the bunch of rows, each containing 
                           the rows in the bunch, each containing the parts of the row
                           (6D).
               s           Combine the ways to split rows &amp; columns into one array (5D).
 m            d            Do the following for each way to split rows &amp; columns (4D):
     m       k                 Do the following for each bunch of rows (3D):
            C                      Transpose the array. We now have a list of column
                                   groups, each containing the row parts (3D).
      m    b                       Do the following for each column group (2D):
          s                            Combine the row parts in the column group. We now
                                       have the list of cells in this row/column group
                                       (1D).
         s                             Sum the cells.
       q1                              Check if the sum is one.
                                   We now have the list of booleans that tell if each
                                   row/column group is valid (1D).
                               We now have the 2D list of booleans that tell if each
                               row/column group in each bunch of rows is valid. (2D)
    s                          Combine the 2D list of booleans to 1D.
  .A                           Check if all values are truthy; if the split is valid.
                           We now have the validity of each split.
s                          Sum the list to get the number of valid solutions.