Friendly reminder that in the UK all ISPs are required by law to keep your entire browsing history for a year, and that history can be accessed by few dozen agencies, warrant free. That's why I use a VPN personally.
If you only use HTTPS they can track your DNS queries but they cant track anything other then that. When you do a google for something so let us say google.com?search=searchTerm they see a dns lookup for google.com. They will not see ?search=searchTerm or anything else. They will see a connection open between your computer and another IP after that. In the future that will stop becoming a problem because there will be DNS over TLS or DNS over HTTPS which will even hide your DNS lookups. Which means all the ISP will see is you made a TCP connection to X. Theoretically they could just do a reverse lookup for that IP but that is not always easy.
Exactly, they're generally more trustworthy than most governments. Security is about probability and is never 100%.
Except that they cant really get your browsing history. Just the domains you used. At least on the 90% of https sites most ppl visit