No, sharing a lawyer is a terrible idea.
Have a look online and see what information is available for your state about where you stand legally. You need information, so that you are never caught off guard with him or play into his hands and so that you can manage your lawyer.
Best advice I ever got when dealing with someone like your H in a legal situation was to ask for the stars even if you don't want them and be prepared to settle for the moon. Because he'll think he's won. And he's going to figure out what your moon is, so pretend like you don't really want it. BTW, check out NPD forums rather than BPD ones. I think you might find them more helpful.