I got worse specs then you (other then CPU which is successor of your CPU) and got around 20FPS and 2D games around 40FPS. So you should have little better results then me
Whilst your computer is low spec, what I suggest you do to increase FPS in editor, is to turn off some of the post processing.
1: Click on “Show”
2: Scroll down to “Post Processing”
3: A menu will popup showing you all the post processing features running.
4: untick the ones you don’t really need.
You will get quite a lot of FPS whilst in editor.
Also if you want to cap your fps not to go higher than say 30fps you can type this into the command line "t.MaxFPS 30"