Lots of people have been using NSSM for a long time so it is very unlikely that it was nssm that was the problem. It is clear that you had a number of issues and that things hadn't necessarily been kept current. You also didn't pay attention to the logs until it was a bit late. There are undoubtedly ways to rotate the logs when the service restarts.
There are also alternative ways to run node.js apps reliably under Windows. It rather depends on the requirements you have. Certainly, using Windows as a server is, in my experience, nowhere near as convenient as using Linux. One excellent way to run Node-RED in production on either platform is behind a reverse proxy. On Windows you can run IIS with an extension that ensures a node.js app is kept live so that you don't have to mess with running it as a service directly. This is typically a lot more efficient.
Also, you probably want to be using jessety/pm2-installer: Install PM2 offline as a service on Windows or Linux. Mostly designed for Windows. (github.com) rather than pm2-windows-service as that hasn't been updated in 4 years.
Please to take care to use current applications and services, you really are wasting your own time and other people's otherwise.
