You condition is getting worse. Unless you can consult a medical professional on the phone, you should go see a doctor. Of course, if you mom won't take you, you're stuck, and either that, or you figure out some other way.
Yes, it does seems to be the count of subscribers for the community on that instance. If you want to see the total number of subscribers to the community, you go to the community's instance (e.g. clicking the !x@y link under the community's name@instance) and look at the number.
With federation, a server tends to have posts/comments for the communities that its users subscribe to. You most likely will get the most comprehensive search result on the biggest instance, which is lemmy.world now. And who knows when it's going to start dropping off old data.
Yes, for home, if you are not installing ad-blockers for all your family members, you can set AdGuard DNS, etc., as DNS servers on your router to somewhat mitigate the ad/malware/scam problem for the entire location.
When I scroll to the very top, I see a drop-down to pick instance/account, notification bell, 3 vertical dot, sort order, and a check box. What do you see?
For Liftoffs, if you go to the top of your feed, you can pick instance/account. The feed that you see is for the account only. If the instance that you picked is offline, you just go to the top and pick another instance/account.
You can search for communities via https://lemmyverse.net/ and see what would meet your need. Good luck.