I would move this to Managed Postgres, if it was my league. My guess is that the Fly Support that comes with that includes giving tips to migrate from the state you’re presently in, although it doesn’t say explicitly that in their official docs.
Assuming that you were looking at the same graph that I’m thinking of, a sustained 10–30% utilization is way above the throttling threshold for a shared-1x Machine. It’s going to be hard to operate at all in that regime…
The official docs describe a procedure for upgrading the specs of a PG Flex node, but that’s the next generation after what you actually have, and I wouldn’t just wing it.