Sure thing. I am using the FCC form 477 data. Unfortunately it relies on ISPs self reporting their coverage data so it may not be fully up to date.
477 data is renowned for being wildly inaccurate. You can find whole articles about how terrible it is, never mind out of date.
Indeed. I wasn't able to verify more granular data doesn't exist but 477 data is at the census block level so I wouldn't expect this to provide anything different from https://broadbandmap.fcc.gov/
Yes. It is a more convenient way to search addresses in bulk. Also makes it easier to identify possible speeds within 500 feet. This is actually how I found my acreage homestead.