Hi! In fact "mal" as an adjective is a short form for "malo" which is the adjective. Example: Olor malo ->Mal olor (Bad smell) The adjective of good is "Bueno" or the short form "Buen" If you say "estoy mal" then "mal" is also and adverb. So "bien" and "mal" are both adverbs in the sentences you wrote. Notice that both words are modifying the verb "Sentir" or "estar" so they are adverbs in both cases. I hope it helps.

"mal" can be an adjective or an adverb. for examples, you can say both: se portó mal/bien; oigo bastante mal/bien (adverb) another example: Fue un mal/buen año. (adjective)