The rawData={“h”:null,”p”:null,”t”:null,”raining”:0} means that the PWS is not sending data to the Weather Service successfully so we have a problem.
Can I check that when you had the PWS connected to the Pi Zero (but before the intercept) that it was sending data to Weather Underground successfully i.e. did you confirm that was the case by visiting your PWS page on Weather Underground and seeing the data update. That would confirm that the problem is with the intercept rather than any infrastructure or the Access Point software.
I assume that you managed to setup the Synology to auto-start the Weather Service otherwise you could just stop the service with a CTRL-C or a reboot of the NAS. If you did configure auto-start then at the Synology command line you could run ps -ax to list all of the running processes and look for any that show something similar to node server.js. You can the stop that process using the ID number in the first column with kill -9 ID. The you can start the process manually with npm start.