Is there an inclination we can give them or a conversation we can have to increase the odds beyond Risktaker and Nature Prevails? I've also been trying to get my subs pregnant to no avail
No, there is no inclination that makes them want to be pregnant. Breeding Kink + Risktaker might increase their chances of letting you nut in them, but nothing affects what they do after in any appreciable way. You're really best off just going about things and if it happens, it happens rather than focusing on it. That's how I found my poly partner pregnant.