For any others who find this later, the solution mentioned in java - How to slow down consumption rate in my Solace Consumer Application - Stack Overflow seems promising. I’ll paste the relevant portion here for reference.
“You can limit the number of messages sent to your application at a time by adjusting both the Guaranteed Message Window Size in your API properties, and the max-delivered-unacked-messages-per-flow parameter for your queue on your Solace event broker. This will control how many messages are delivered to the API before receiving either a transport acknowledgement, or application acknowledgement.”