Your encryption greatly increases the complexity of the seed at basically no benefit. There is already a feature to have an extra password alongside your passphrase built into BIP39.

Note that BIP39 words are picked to be relatively distinguishable from each another so even a misspelling or vague letter is recoverable. In contrast, your encrypted seed phrase is a mess of upper case, lower case, letters and symbols.

I changed a single letter in the encrypted seed phrase from lower case to upper case (something that is very likely to happen if someone writes it down), and when decrypted it completely broke without any warning that there was an error in the phrase.

This is less than useless, this is a dangerous piece of software that WILL make people lose their seed phrase.