" it appears Turbotax is adding in interest and dividend income into our AGI and basing the over contribution on that higher amount."
TurboTax is behaving correctly. AGI includes interest and dividends. MAGI for this purpose is not permitted to exclude any income from AGI other than the taxable amount of taxable conversions or rollovers to a Roth IRA. MAGI is not just W-2 income.
It seems that you have indeed made excess Roth IRA contributions.
