You have copied data from the supporting reference tables to tblFixed Category. This would appear counter to good database design - ie database normalisation principles which are employed to overcome redundant data issues. You should only have one copy of a data item. Your forms and reports can draw this data in using the appropriate query. Modify tblFixed Category to remove the fields: Type, Route, Category and Revenue.
This is the source of your original issue I think. You are writing to the tblFixed Category via form adding "route" information, however the Route does not exist in the tblRoute (which has RI established between them via the RouteID). The form has as its record source the table Fixed Category.
The form then needs to be adjusted so Route is a combo - selecting from the list of items in the tblRoute - just as you have done for CategoryID. Remove the other Category combo - it is using a value list which is a duplicate of values in tblCategory and accessed/display via the CategoryID combo. Repeat this for Revenue.
See how you progress to this point before moving forward. Good luck.