can 1 Notary witness my last will and testament in Ohio

You are unable to notarize your own signature as a matter of law.  Notaries are often used to help avoid hearing or litigation in the future.  However, notarization is not a per se requirement to create a valid Will.  See Section 2107.03 of the Ohio Revised Code.  As long as two witnesses can attest to the required formalities, the Will should be satisfy that provision of the law.