Yes, you do have the correct motor. The C48K2PA105 had a total HP rating of 1.25. That is the same as the UQC1102. Your existing impeller and diffuser are properly sized for the UQC1102.
The sound from your multiport valve is usually caused by air in the system. If it doesn’t work it’s way out and continues to be a problem, I’d look for a suction side air leak.
Another cause of a rattling sound in the multiport valve is a bad spider gasket.
