{romuluSngan HoS law' qarDaSngan HoS puS jay'}

The first question is "can we place the {jay'} on a law' puS
construction ?".

No reason we can't.

Does the construction above mean "the #!@! romulan is stronger than
the cardassian", or does it mean "the romulan is stronger than the
#!@! cardassian" ?

Or does it mean "the romulan is #!@! stronger than the cardassian" ?

Or is it that we can't apply the "#!@!" to only one part of the
comparative construction, or any kind of sentence ?

jay' turns the entire sentence into an invective. It does not apply invective to any single part of the sentence.

-- 
SuStel
http://trimboli.name