0. You know that all your replies, code and webpage look extremely like AI outputs? If this is the case, it would be way better if you are open about using such tools.
2. Meaning that encryption is way slower than decryption.
3. You are making this concept quite confusing. Path collision is inevitable because you only have two options to choose from, making it easy to get collisions. Round-key collisions are something different and merely depends on how you effectively derive such keys. I might be wrong because I would need time to think about, but I believe that to get a "catastrophic key reuse" you would have to get the same state, the same inputs for the round key derivation function, the same ciphertext to be used and, most probably, some additional information a-la chosen-plaintext to effectively get something out that would break that specific chunk. Since you claim you have some ratcheting mechanism, push the attack to other rounds might not even be possible. If not, then you might not really achieve forward secrecy.