Hi,
I'm Kishan, a full-stack web developer. Please have a look at my profile and reviews to know more about me.
I've studied your project requirements, and I think SSE is not the right answer for your problem. If anything SSE will increase load on the server since persistent connections need to be maintained for all clients. If you would like, I can help you scale your infrastructure and optimize your application and/or supporting architecture to get more performance out of your website.
Please let me know your thoughts.
Regards
Kishan