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She is NOT entitled to a full 1/2 of your 401K unless you established the 401K at the time of the marriage and not before marriage and the funds put into the account were all from during the time of the marriage. If that is not the case, then under OH law, she would only be entitled to 1/2 of the 5 years of marital funds put into the 401K which is considerably less than 1/2 of the entire 401K.
You also do not have to pay spousal support or COBRA for her based on this being a very short marriage of 5 years. At the most the court would order spousal support temporarily for usually not more than 5-12 months. So anything in that range you can agree upon would be fair.
If she is under employed, this could hurt her in court as this can be grounds for a court to refuse to award her support and she needs to understand that as well as it would be a bargaining power for you to negotiate to accept a little less if she is not willing to be reasonable.
As we do not know enough about your assets and cannot get that information in this forum, we cannot tell you exactly the amounts of support but in general it would be subtracting your net monthly income from her net and then 25%-50% of that difference for monthly temporary support.
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