Ok so, first of all, the destiny knot passes down 5 random ivs of the parents (5 in total from both, not 5 each) to the baby pokemon. The power items, as I'm assuming you already know since you mentioned the buneary is for HP and it's holding a power weight, can each be used to pass down a specific stat to the baby mon. The rest are assigned on random. In theory, you could just keep doing what you're already doing over and over until you get lucky enough for 4-5 of jynx's stats to be passed down and maybe be the right ones, but honestly that can be extremely time consuming in some cases, so it's best to use a ditto.
Now, since you're at 6 badges, you should already be past the point of being able to obtain the first ditto. I'm assuming you might have missed that since you didn't mention it, and I'm not sure if you can still go back and get it after leaving that place as I haven't tried that before myself. At this point, I would normally just offer you to breed you a smoochum myself since I've managed to get a perfect iv ditto, but as you've mentioned that you've found breeding to be quite enjoyable, I can instead try trading you my ditto from an older save file.