This experience is amazing, and it has a large chance of becoming a VERY popular experience. The only issue (as you’ve stated) is the major FPS drops. Here are some topics that might help you optimize the experience! I look foward to playing this once it’s optimized more!
I encourage you to not give up, burn out can be a major problem when developing an experience, but once you take a break and overcome it, it can be the best feeling in the world. You have a popular experence at the grasp of your fingertips, all you need to do is optimize and keep going! You can do this, friend! 
Optimization Links!
And also, your experience is super realistic and pretty! I love how nice it looks!
Even the city lights turn on at night!
