How to increase the number of simultaneous TCP connections of Load Balancer.

The maximum number of simultaneous TCP connections is set for each instance. Therefore, even if multiple interfaces and IP addresses are used, it does not change.
Although it is possible to raise the upper limit by purchasing multiple instances, it does not guarantee performance because it is a shared service.
If you want to guarantee performance, please select dedicated type service such as Baremetal Server.

Please refer to Measurement Result of Load Balancer Performance here.