Amur Maple?

HI Folks,
Assuming that this is an Amur maple is it to late to cut it back nearer the trunk now? Or wait until winter? I have cleaned off the moss from the trunk and cleared all the weeds and Moss off the soil. The soil is not great and I plan to repot next spring and see what the roots are like then. I know it is a bit of a tatty tree and will probably never be stunning but I am sure I can do something with it. Any help would be Greatly appreciated.

https://www.dropbox.com/s/p0bx09al9jmlu35/20150821_173741.jpg?dl=0

https://www.dropbox.com/s/x1i9dtfiv3od9md/20150821_173911.jpg?dl=0