I've published a few (bad) games to Google Play, however I've never messed with Admob or IAPs because I don't really care about revenue. I have put the Google Play Sign In system into one of my games, though, and it was a pain, but that's just because I'm dumb. I eventually got help in the C3 forums.
I'd say it isn't too difficult to publish, and it gets easier over time after going through the process for each game. On Construct's side, it's way too easy. Just export (although certain settings do change things like the app name, so make sure you correctly set every single setting to work, including the Icons folder), and then download the file. Most of the struggle comes from Google's side, mainly because you have to just give a lot of info about the game, make a privacy policy (i just used Termly), and a lot more.
When it comes to the links not working, that simply could just be because the dev took down the game, or like you said, maybe Google took it down because of requirements.
There aren't too many requirements for maintaining the game, however I did recently get an email about needing to update my games to also target newer versions of Android (except i never did that because honestly i dont care if the games get taken down they suck :P)
For screen scaling, I've never cared. I used Letterbox scaling so it simply just has black bars on extra space.
I know a lot of my answers were just "oh I ignored that" but that's because I made those games a while ago when my C3 skills were still okay at best and didn't care about making a great game, I just wanted something I made to be on my phone :)
idk how helpful this is for you but I might as well give my input.
also sorry for so much reading I tried to answer as many questions as I could.