Address the job, not just the résumé.

Some do. Recruiters often skip them; hiring managers at smaller places read every one. You can't tell which you've got, so: your résumé has to work alone, and the letter has to be worth it if someone does open it.

Three short paragraphs. Two hundred words is plenty. It's there to say why this job and what you'd bring that the résumé can't show, not to repeat the résumé in sentences.

"Dear Hiring Team" is fine. Skip "To Whom It May Concern", it reads like a form letter because it is one. Don't guess a name you're unsure of.

Skip it unless you've got something specific: a real reason you want this one, or context your résumé raises but doesn't explain, like a career change or a gap. If it would just paraphrase the résumé, optional means optional.

Reuse the shape, never the details. A letter that could've gone anywhere reads exactly like that, and the giveaway is always an opening that shows no sign you know what the company does. Changing the company name isn't tailoring.

Only if they asked. If they did, give a range and say you're flexible for the right role. Volunteering a number nobody asked for anchors a negotiation you haven't started, usually against you.