The error you are getting about the filterdef is because you have the include further down on the page.
Move this code to the top of the page:
//WA Database Search Include
The other thing you mentioned was that you are using OR as the separator, you should use AND so that the results or exclusive to the rates you enter. If you have the two criteria separated by OR then you will get any results that are greater than the first value, or less than the second. You should have both criteria separated with the AND so that you will have values that are greater than the first entered value and less than the second entered value.
Other than this the code on the page looks like the search is setup correctly. Please make these updates and test the page out again to see if you are getting the desired result.