Well MSSQL is a heavy hitter but it would appear you have things handled from a hardware perspective.
140 queries/sec is basically almost no traffic at all for those spec.
You could change the max connections to -1 that would allow it to take as many connections as it wants.
After, as a test, I’d disable the secondary connection and see what happens.
I’ve got a couple of db connections that stay steady 2 to 4 connections but can burst as high as 30 under load (reports) and had to set the connection limit to -1.
As a side note I’ve got several projects (more than 30 active) on the same gateway and I made the decision a couple years ago that each project would get its own db on the same mySQL engine. This allows me to break up connections by project. Please keep in mind that I don’t know anything about your organization when i say this but, since Ignition allows me to pull from any db location across 30+ projects, is there a way that you might be able to compartmentalize your tags so that you could spread the load across multiple logical connections. Just a thought.