Nothing, but keep in mind that maybe 95% or even 99% of the fediverse users are a bunch of nobodies. To have a stalker or someone trying to impersonate you, you would have to be extremely lucky (or unlucky)
For todos, I'm currently trying out todoist. It's like Todo+date (can be repeated like every day/week etc)+priorities and a few tags and stuff. I can't say it works for me nor that it doesn't work, it's been a few weeks only, but a trick to somehow make it work (I mean like use the app to help you accomplish stuff and not delay it) is to write down everything: fold the laundry, wash the dishes... And then organize them when you feel like it, give them a date so that you do them when you need to. I look at the app every morning to know what I have to do, and just doing things to mark them as done feels good (tho I must admit that I let a few todos roll over multiple days because they are daunting tasks but at least I do them).
For notes I have had Google note but it was hard to organize them and find your way through. Now I use obsidian at work (miss colors and tags but there is markdown and folders), and notion for personal stuff. Notion is great but my database is growing quickly and even if I love organizing it and could spend days just putting tags, folders, colors, arranging everything to be perfect, I feel a bit overwhelmed because, well, it's huge. I may need to make a central hub page with links to everything I use frequently?
It means that you need to log back in, because the server forced you to disconnect.