Having just watched some Atom Ant cartoons for reference I wouldn't want to eat the guy. He'd just burst from my chest and clobber me. And if I chewed, I'd break my teeth on him.
Dude no-sold a karate chop from another bug who was capable of flinging human chairs at him. That's a decent level of force concentrated into a tiny area of attack, far more than my teeth are capable of outputting. And given what some of the other posters are saying, this is a
low-end durability feat for him.
In the same cartoon, Atom dodges an attack from the karate bug by zipping away in mid swing, vanishing from the screen to the extent that it appeared to the karate bug that he'd been obliterated by the attack, when in fact he'd just gone to the other side of the dojo to throw a trash can at the guy.
Meanwhile, strengthwise, Atom does things like
casually stop a helicopter that is carrying city hall. Catching bullets, flinging pianos and lifting cars, trivially. And similar stunts.
So, it looks like even if Knuckles has the strength feats, (which he may or may not) Knuckles just isn't hitting or dodging the guy, and he's going to need some
mean durability feats to keep from having his head torn off.