Design a custom homophonic substitution cipher for the English alphabet. In this cipher, single high-frequency letters (like E, T, A) should map to multiple different symbols to obscure frequency analysis. Create a key for this system. Then, encrypt the following message: 'The swift fox jumps over the lazy dog under the midnight moon.' Provide the encrypted string only, followed by the logic and key in a separate section. Ensure the symbols used are a mix of alphanumeric and special characters.