About step #1 above.., in my case, I found that stopping the SW services on the core and the polling engines does not work. The services come back online automatically a few minutes later. Still, I prefer to make sure that the database is not being updated while I do the full SQL backup. So, I end up having to stop and disable the SW services on the core and polling engines and then re-enable them after the successful SQL backup. On this note, I recommended for SW to allow a Maintenance Mode feature in SW, stopping ALL services until told otherwise.
Also, I did run into an issue where the Config Wizard failed due to files locked by the website. I called SW tech support and they recommended for me to an one additional step, to run IISRESET from the Command Prompt. The additional step, per SW tech support needs to be done just before step #5 above. So, I guess you can call it, step #4b -- To run IISRESET from the Command Prompt. I did as SW tech suggested and that was the only way that I could get the Config Wizard to run. Aside from that, I did not find any problems with my NPM and SAM upgrades.
Best wishes.