In case someone gets one of my packets, they wouldn't be able to steal my money, but they would be able to monitor my transactions. I know that's not the best approach, but I can live with it!
There is a simple way around this. For any
m-of-
n multi-sig, then you only need to back up
n minus
m number of xpubs alongside each seed phrase (provided you pick the correct ones) and still have full redundancy and yet also protect your privacy.
For example, using your 2-of-3 system, then you back up 3-2 = 1 xpub alongside each seed phrase, and your 3 back ups would look like this:
Back up 1: Seed A, xpub B
Back up 2: Seed B, xpub C
Back up 3: Seed C, xpub A
As you can see, the compromise of any one back up is insufficient for an attacker to spy on your wallet, while you still only need to recover any 2 back ups to have all the information needed to restore your wallet.
Actually you were the one who taught me this system. So I owe you many thanks!
In general, let's conclude that there is no point having a n-of-m system, where many of your keys are stored online. Ideally, you want none of them to be online.
Finally, let me give you an alternative, which I think is still better than your current system.
I keep suggesting people to create a fully offline wallet and add a passphrase. This is more than enough, unless of course you want to learn better practices, which is of course advisable, but not necessary.
You could back-up a simple singlesig wallet with a passphrase and maintain 3 vaults and split the backup as follows:
vault1: words 1-6 + passphrase
vault2: words 7-12 + passphrase
vault3: words 1-12
In this case, losing one of the vaults wouldn't lead to losing your money. Only 2 of the backups are required to sign a transactions. What you gain with this system is that you wouldn't have to trust your memory at all. You have everything backed-up, even the passphrase.