We have experience of 5+ years in Wordpress development. We are specially specialized in WordPress speed optimization and code minification. We are glad that you had all those tools also we were sad that you cannot make much out of those tools. We not only use those tools but also minify the codes, reduct HTTP request, enhance your server, and optimize the images. This will obviously make your server fast.
Our last client on this platform was also similar to you. Your website loads in 12 seconds as you mentioned, but his used to load in 25 seconds. After our optimization, his website now loads in under 3 seconds. Not only that, we have managed to load the sites of few of our clients in under 1 seconds also. We can make your site load in under 1 seconds too, but this will depend on your server's specs. However, we can still guarantee you to load your site under 3 seconds.
We would be glad to talk more about the project. Please send us a message to discuss about this project.