You can re-size the width of the fields by placing your mouse right where the field name and the field value boxes touch and dragging to the left or right as desired. This setting should be saved, so you shouldn't have to do this every time you open the attribute editor.
I can see what you mean about the lock icon. I'd suggest that you go to the ArcFM Product page and submit an idea to get this changed. This is the sort of thing that our developers will see and hopefully can change easily if it gets enough attention.
Let me know if you have any other issues!
I am able to resize the column width but it does not stick even within my current session. I resize the column then select the same object again and the column width reverts back to the previous size. Is this size set as a default somewhere that can be changed?