I was treated badly by this horrid guy - now I find out that he plans to lie to get out of national service..?

Look honestly you need to just drop him. Let me see, he keeps feeding you crap and you keep eating it up right? Drop him. Leave him. Don't get mixed up with him cause if anything was to happen then guess what, you knew and you didn't do anything. This guy is playing you like a fool and your letting him. If he really cared about you he wouldn't hurt you.