Secondly, the failure to produce the will in a short time is very likely a violation of a petty criminal law and might result in prosecution and imposition of a small fine. If that can be achieved, you have a big leg up in a civil suit for fraudulent concealment and other forms of fraud. The statute of limitations may well be suspended during the coverup.
Third, what happened to the proceeds of any property transfers? Either these relatives volunteer with satisfactory documentary proof or sue the one(s) responsible and depose all concerned to force early testimony under oath. If you sue, attach their real estate and obtain an injunction freezing their assets by a pre-judgment remedy to be served with the complaint in the lawsuit. Seek multiple damages and/or punitive damages as the law may allow for leverage and, perhaps, for punishment.
Finally, since I am not at all familiar with Michigan law and am not licensed to practice there or anywhere since I am now (hank God) a recovering attorney, the foregoing is just a bit of a partial roadmap. You must obtain the services of a thoroughly competent and experienced estate attorney. The cost can likely be paid by the estate.
Nothing in this post should be construed by you, your husband or anyone else as legal advice. Be guided by a wise and aggressive attorney and expect him/her to keep you informed regularly at every step of the proceedings. Carefully review any written retainer agreement by which you hire the lawyer to make sure that there will be no controversies. You make the policy decisions. The lawyer advises you and chooses appropriate procedures or lays them out for you to choose with full explanation and advice and time to decide.
Good luck in your 'recovery'!