I couldn’t find anything to directly support the idea that RDxS/S45 is triploid (only possibly passed down from ‘New Dawn’–otherwise, the other roses in its background are tetraploid), but it does sound like it might have issues with producing seed based on this older thread:
I’d definitely focus on RDxS pollen, and it sounds like it releases that rather early, so maybe collecting anthers before the buds fully open, possibly even the night before, would be a good tactic.
Luckily, ‘Lykkefund’ loves to set hips full of seeds (without caring too much about the pollen parent ploidy) and germinates easily. The only serious threats are cane borers and maybe rose seed chalcids.