Beano is a digestive enzyme, not an antacid. Unless you have heartburn, there shouldn't be any need to take antacids. And if you don't need them, they're NOT a good way to get calcium! (They can also act as a laxative, too).
There isn't necessarily a *single enzyme* that we require to digest soy and it might be different in different people. Your best insurance is, before meals, taking one or two complete digestive enzymes (which means it can help you digest carbs, protein and fats - I THINK beano has this but it might just be carbs, not sure since I've never used it). This is something you'll probably want to try anyway (if you haven't already) just as a general IBS remedy to help with your bloating.