Translation:He watches only romantic movies on Mondays.
I think that's right. LenReed's comment seems to confirm that. The question in the exercise that brought us here has que before romantic films, so the thing being limited is romantic films. If the thing being limited is Monday (eg, watches romantic films but only on Mondays) then que comes before le lundi.
That said, I'm stumbling in the dark as much as the next person.