Good thing that I was able to implement it from scratch on Amethyst (including ChaCha20 itself) so, the audit + my own knowledge was enough to make me very confident in the approach.
Also, in 3 year...
Except my key point: if I loose my nsec. Almost nobody in the bitcoin community fully trusts their nsec / seed phrase except in hardware wallets. We are constantly told to keep our seeds offline. Marmot solves this for PMs.