So, generally speaking, all eggs inherit 3 IVs in any random combination from their two parents, with the remaining 3 being completely randomly generated. Destiny Knot being held by either parent changes the number of inherited stats from the parents to 5 and therefor causes only 1 to be randomly generated. It is *possible* to roll your 30/x/31/31/31/31 Smoochum from this pair of parents, but the odds are slim when Buneary only has one stat you want and none of the others. In order to have generally better offspring, you need to have generally better parents.
Your problem here is that Jynx is a female-only species, so you will never get a replacement father just by breeding Smoochum.
The solution is breeding a perfect 'mon of some other species first, a species that can both be male and is also compatible with Jynx's egg group.