I think you are going to have to do a better job explaining the scematics... It might just be me, but all I'm seeing is a bunch of coils and diodes and I have no clue why you need so many of them in parralell, or what they are even supposed to do. Also, I don't seem to understand what you have all the ideal AC and current sources for... not to mention that if I'm reading it right, in the last schematic you are connecting the 12V and 50V rail to the same point, which won't work...
I would like to add that your motor will probably be fine with 50V, but I don't really see the point of pushing it past spec...