as you said, take a step back and whiffpunish with hados or sweep / whatever.
If you can do that often enough, so that your opponents gets aware of “everytime I throw something out I eat damage”. You can start dashing in once in a while, because he’ll get nervous about sticking out buttons.
But reactionary whiffpunishing is really hard, if not impossible in this game, you should either try to preemptively use buttons with a lot of active frames on them or “force” buttons from your opponent.
Find out at what point he presses which button, for example you walk into cr.mk range, immediately walk back and cr.mp->hado
If he pressed cr.mk you’ll stuff his button and can dash up behind that hado. If he didnt you whiffed a button just outside of his range, not too bad/ punishable