Unless you expect poor rate of return, this chart seems to show that taking the lump sum is the way to go. I would suggest this:
1) put approx half into conservative fixed income and use that to take most of the required income. SS being the other main contributor now for OP's SS and then supplemented with DH's SS in 5 years at 70. This $314k should last well past 10 years, depending on rate of return and withdrawal rates There also might be some adjustments for taxes, see number 2 below.
2) put other half into equities (broad based fund type) and let it ride with dividend reinvestment until it is needed for income. If this [half of $6128k] is in taxable account, then it might be advantageous to take the dividends as income, with their favorable long term gains tax rate. If you use the long term market return avg of approx 9%, and the rule of 72 [divide 72 by rate of return gives time to double], then this will double after 8 years, and increase more depending how long you let it ride.
The best part of not having an annuity is that you can always access the principle if needed for an unexpected large expense. Plus assuming you get a reasonable good rate of return on the equities side, you should have plenty of money left over after 20 years.