My advisor and I have mutually agreed to dissolve our agreement. What should I have him sign to make it official? Is there a standard template for this, or can I just have him sign a resignation letter of sorts?
Take several things in your mind: benefits, closing deals, Distribution of utilities and over all, resing any liability consequences in future after finish your relation with your ex partner
Don't try to be your own lawyer, there are a lot of contingencies that you should at least consider. At least check with your local law school, see if they have a Clinic you can use for a low cost. I teach at the University of Akron and we have one. I think Cleveland State and Case Western do also.
Make reference to the initial agreement, their should be a clause about termination ,well if none , I advise you get a lawyer to prepare a contract termination agreement.