Yup. You can check a lot of stat about a node on tor website. https://metrics.torproject.org/

Most of the nodes are hosted by Tor Foundation itself

No. Use it for everyday tasks. If Tor is used by only people who need them, they will be easily detected. The whole reason US Navy released Tor to public was so normal users can scramble the usage detection. One more advantage is that right now lot of website block tor users if more users will use tor then they might stop it.