If the 3rd party tool was EZSQL, then download a new version. An option was added last week so that when you are extracting the DDL for a lot of tables, the FK constraints are all at the end of the script so you won't have errors.
You may have to enable the feature under 'Preferences' -> 'DDL Extract'
If your concern with the DMP files is because you are going from one OS to another, don't worry about it. It should work. If your concern is that you don't want data, use the ROWS=N option.
You have to install the 8.0.5 export views into your 8.1.5 database, then use a 8.0.5 client to run the export. You can then use the resulting file to import in an 8.0.5 database. Then of course you should set your 8.1.5 db back to normal. I believe the name of the script is catexp.sql.