What does the score mean?

It is issues per 100 words, not a raw count, so a long essay isn't punished for being long. 100 means nothing was flagged.

Why do some issues have no suggested fix?

Because an honest one doesn't exist. "Think outside the box" has no drop-in replacement — the fix is to name the actual idea, so the tool says that instead of pasting advice into your document.

Can I turn off a check I disagree with?

Yes — tap any check in the list to mute it. Adverbs and passive voice in particular are style opinions, not errors.

Cliché, Filler & Passive Voice Finder — Free and Private

Find the clichés, filler words, hedging, weak verbs, passive voice and repetition in a draft, underlined where they are, with a concrete replacement wherever one honestly exists.