In regards to the FPS are you maybe not destroying objects when they go off screen?
Viewing post in T.T. the Evil Physics Teacher comments
I do. Though I guess I only destroy it after they go some distance off screen as there are some bullets that have a possibility to re-enter due to their trajectory...
Though I just realized that unlike my previous game this was recycled from, only one type of bullet this time has a possibility of re-entering the screen (the fire), and even then they only need a small margin. I'll see if reducing the margin a bit will fix the lag.