Do you feel bad or badly? Some more of my reference ...

Do you feel bad or badly?  Some more of my reference booksI think most of the confusion comes with describing how one feels. Try substituting a synonym or antonym, an –ly word for badly or an adjective for bad. If you mean condition (the adjective), an easy way to know is to substitute good for bad/badly. Here are some examples of the condition: He woke up feeling bad (good). He ate the leftover shrimp and woke up feeling badly/goodly. (Unlikely, unless food poisoning damaged his hands during the night.)  But she felt bad/badly ( good/goodly ) about what she'd done. He felt bad the morning after the party. (He'd probably overindulged.)
My favorite reference bookBadly, the adv, modifies a verb, adj, or other adverb. Badly is seldom used with feel or felt. Badly tells how. If you're referring to how as in the tactile sense, try substituting clumsily or awkwardly. He felt badly (because his coordination was impaired). Because of the frostbite damage to his fingers, he felt badly; he was unable to tell skin from cloth. He played the piano badly these days. (It tells how he played) He felt clumsily or played awkwardly. 
Felt badly is not common usage, at least not that I know of. It's almost always going to be felt bad . But maybe I'm missing something--feel free to say so.
With was, the correct word is much more obvious. His behavior was bad/badly (offensive or offensively?). Her grades were bad/badly. (Unacceptable/unacceptably?) He behaved bad/badly (offensive/offensively).  This tells how he behaved.
You may think of other examples that are much clearer or uses I haven't thought of. Or some fun uses. Please! Let me know. 
Next week I'll tackle lie, lay, lain. Won't that be fun?