These are all my suggestions, I would also add look for ways to spread out tasks to other smaller VMs - the general pricing is +$5 "per" ($5 per +1 vCPU, $5 per +2G vRAM), a $5/$10 webserver only handle static asset delivery, then apps on middle tier app servers at $15/$20 would give better fault tolerance and spread out the load and still keep blue/green.
* replace the currently inactive server with a smaller instance
* swap to the new instance and test the load
* replace the second server
For such a small app I’d drop the blue/green (most deploys will likely only take a few seconds?) and host Postgres on the same server.
Also, I’d move metabase onto a DO instance.
Any reason you’re using DNSSimple over a cheaper provider (or free in the case of DO)?