Okokok calm your tits.
Firstly, chickens will not spawn because
[insert "you're doing it wrong" meme here]
I know MD better than that.
Secondly, any explosion is dangerous because I'd have to find a way to cancel it in Kanto, Johto, and randomAssLocationAdminsMadeForFunInTheWild.
Thirdly, making it only do damage, is PROBABLY possible, but I'd have to tinker.
Fourthly, I wouldn't use an egg, I'd use an enderpearl or an unused splash potion, since the tossed trajectory would be more realistic to an "egg bomb."