I think the issue is that the webhook is sending one request at a time so the split batch is not really working since there is nothing to split when the call is sent one at a time. maybe I need to store all the data in one place then run the split batch to slow down the process.
does that sound about right?
Next to running n8n in main mode as @RicardoE105 did hint or running n8n in scaling mode to increase the throughput, you could do something as you did propose. Like having a workflow that pushes things to a queue and then another one that processes those queue items.