my dad died 3 weeks ago and Nationwide says his policy still lists his ex-wife (my mom) as beneficiary from their 2009 Ohio divorce - what are my actual options here

not really sure where else to ask this and the funeral home director suggested looking online. my dad passed pretty unexpectedly last month, heart attack at 64, no warning. me and my sister have been trying to wind up his affairs and one of the things we found was a Nationwide term policy from 2003 for $250,000. its still in force, he was making the payments out of his checking account every month.

called Nationwide last week to start the claim. the rep told me the named beneficiary is my mother. my parents divorced in 2009 (Ohio, contested but eventually settled, both remarried since). my dad remarried in 2014 and was still married to my stepmom when he passed. we always assumed he had updated everything but apparently this policy was overlooked. the divorce decree, which i have a copy of, says "each party shall be solely entitled to all assets in their name as of the date of this decree" but does not specifically mention this policy by name.

here is the messy part. my mom is not a villain. she did not even know she was still on the policy. when i called and told her she was honestly surprised and said she would "figure out the right thing to do." but i also know my stepmom is in a tough spot financially after the funeral and the lost income, and my mom is comfortably remarried and definitely does not need the money.

questions:

1) does Ohio have a "revocation by divorce" statute that automatically removes an ex-spouse as beneficiary on life insurance after divorce? i have read conflicting things online about whether it applies to ERISA policies vs private policies and whether the divorce decree has to specifically reference the policy.

2) if my mom decides to disclaim her interest (basically refuse the benefit), does it go to a contingent beneficiary (none listed, i checked), to dad's estate, or somewhere else? does she have to do anything formal or just notify Nationwide in writing?

3) if mom keeps the money, can my stepmom contest it? on what grounds?

4) should we just be calling a Ohio probate / estate attorney instead of trying to navigate this ourselves? i feel like we are over our heads.

thanks for any guidance. this whole thing has been awful and the last thing any of us wanted was to be arguing about money on top of everything else.