It’s always possible that an in-browser update will unexpectedly fail, so you should always choose a time when you can suffer the downtime you might need, and you can then fall back to a command line rebuild. (And you should take a backup and download it before you do anything.)
Sometimes, rarely, it can help to reboot the machine, especially if it has been running for a long time - a year or more - since reboot. You should also be applying package updates for security reasons, often they will advise a reboot.
I wouldn’t expect any great advantage in doing the swapoff/swapon but maybe it does no harm. Any space that you’ve apparently reclaimed can only have come from RAM, will probably have just cleared some caches, and they should have been managed automatically.
The real problem is that your 1G RAM + 2G swap was not enough. There’s a current thread about whether requirements have recently changed:
Have Discourse’s requirements changed recently?