serve reliably relevant ads/product/youtube recomendations
discover when I arrive at home or go to bed
I personally cover the web camera that conveniently came built into my one laptop just in case. Also watch your habits, don't go to a particular site as soon as you get home and don't come home at the same time every day.
flag me for reading dissident articles and watching DIY video about gas masks
Using a VPN or TOR along with not using a personal account would work with this also make sure to scrub the metadata from any file you upload here is a good place to start looking into metadata removal.
flag me as the user that hogs most traffic from my ISP
flag me for using VPN/TOR
If you don't want your ISP to flag you for anything then don't do anything that could cause you to be flagged on YOUR internet connection. Use a public hot spot or a neighbors wireless connection (with permission of course :)).
Also on the VPN front while there are many VPN services out there. However it's plausible (probably not likely) for a site to compile a list of IP's that would come from that VPN provider. What you could do is rent a cloud server, setup your own VPN and use that.
You might also be interested in TailsOS it (supposedly) runs all internet traffic through tor and privoxy. If I really want to have an anonymous session I hookup to my VPN on my base machine then run Tails live in a VirtualBox.
Hope this helps