最近なんだかぼーっとしてる is excellent.
I would say なにやら反応したようだね for "I saw you reacted (to this) somehow". (Actually, どうやら is a better translation for "somehow" alone, but どうやら反応したようだね sounds more of "Looks like you reacted" than "you reacted somehow".
何{なに}やら is an adverb formed by なに + やら. I can't give you the exact grammatical explanation for やら, but it helps to add "vagueness", "haziness", "obscurity", "uncertainty", etc.
やられる is the passive form of やる. やる corresponds to "to do" in the very general sense (or if you know Latin, it corresponds to "agere".)
反応したようだった vs 反応したようだ
This is hard to explain. I have the impression that 反応したようだった corresponds to "looked to have reacted" and 反応したようだ corresponds to "looks to have reacted".