It is an MPE patch, so midi channel 1 isn't going to work (that is the master channel, the rest are for notes).
The noise issues doesn't sound good, though! I don't have any clicks, but when I first tried doing a Mellotron patch using the factory/wave/play object I had ugly clicks whenever a sample was playing and a new one was started. What I believe was happening was that when the sd-card was busy seeking the start of the sample data, the thread responsible for reading from the sd card took so long that audio rate cycles were skipped. Hence the clicks. So I bought the fastest sd-card I could find. When that didn't appear to help, I made the "polyplay" object with lower thread priority. Which fixed it. But I didn't go back to try the old, slow card. So I don't actually know if a sd-card with poor seek time will cause problems. It seems likely, I guess, but it could be something else that is wrong and just happens to work out on my specific card.
I haven't noticed any distortion, but to rule that out it is probably worth it to attenuate the audio from the polyplay object, just in case.