I had a male and female together also. They weren't really "gentle" but they didn't kill each other. They laid eggs several times as well. Do you have pictures?
Danios don't need and shouldn't eat feeder fish.
Infact you shouldn't feed ANY fish feeder fish unless it's nessesary for their diet. Feeders are a quick way to introduce parasites and disease into your tank unlees you raise them yourself.
i got them from my lfs and they have the healthies fish,they even have a quarantine tank how many wal-marts,petcos and petsmarts do you see that have that,and the feeder fish were for my female and male betta
If he's bored that doesn't mean he needs to eat a fish though. Please keep in mind these are fish that eat mosquito larva. Their stomachs are the size of one of their eyes.
The best thing to do when your fish are bored is to rearrange the tank or add something new for them to explore. Betta's though, particularly male bettas actually like to just float in a plant and be lazy little lions lording over their turf. They live longer when they're calmer. Having them puffed up and flaring all the time is stressful for them.
Adding some dither for them to chase after now and then is one thing but throwing in a fish and expecting them to kill it and eat it really isn't reasonable. Even if he did kill it it would rot in your tank and pollute it.
I personally wouldn't bother feeding anything live (except maybe blood worms but I haven't yet) to my bettas. They seem perfectly content with their freeze dried blood worms, betta bites, and flake food. I'd stick with that. Why are you trying to feed him live food anyway? For your entertainment or for his health?