If someone else gets 2 or more of my seed phrases, will it harm me?
As mentioned, it doesn't hurt you, as there are still a few more unknowns. But it's better for others not to get any of the seed phrases.
How can I make my seed phrase more secure?
I'm not including a link to this related post because it's been abandoned, but basically, I'm saying to store the seed phrase in a place that's fireproof, floodproof, or prone to breakage or being easily erased by something.
The material used to write the seed phrase must undergo all tests for its durability.