You would save the exchange fee. Call CME membership, they will email you the forms, Buy seat plus $2k admin fee, email IB and they will adjust your commissions.
On the dave Ramsey thread on Reddit they have modified the program. Skip mutual funds and do index ETFs to save the fees.
How big is Dave Ramsey in the US? I only found him on YouTube as I live in London.
If you want to do more than 500 contracts on stock options or less on SPX then call the Interactive brokers desk in Chicago and they will shop it for you. Number is on their website.