1. You must split your coins in 2-3 wallets, to avoid losing all your coins if they are all in one wallet.
Storing your coins in more than one wallet doesn't give guarantee that your coins are well secured despite using non custodial wallets, but all depends on how you provide your non custodial wallet with strong securities, by keeping your private key and seed phrase safely. If you keep your found in different wallet and does wallets is no well secured you can lost all your funds also. All i know is that provide your wallet with strong securities and your found will be safe always.
5. You find a place to store the backups. But then you are not sure if the backups are safe.
Yes, it is true that we store our backups and we are not sure that if the backups are safe due to where we store them, but you can be 90% sure if you store them in ways, and that is why they use to advise us to always hide it privately where it will hard for any to find it expect you and who tell about it.