Well, how much life insurance can you get for $800/month?
Alternately - invest the $800/month difference. Assume 8% return.
Obviously, the longer he lives, the better off you are. At age 50, male life expectancy in the USA is age 81.5. Assume he's average.
That's $1,800,000 you accumulate by the quickie online calculator I just used.
Figure a Safe Withdrawal Rate (SWR) of 4%. That gives you ~$6000 you can withdraw from that lump sum each month.
Hmmm..... That worked out a little too neatly.
$4,000 from the residual pension + $6,000 from the investments means you keep going with $10,000/month perpetually
So, two approaches listed there.
Really, a heck of a lot depends on your health, his health, et cetera.
For an "average" person, it looks like the Option A is the better choice - especially if you are Moustachian in your approach.
If he has poor health, and you have great health/are much younger.... maybe Option B.
Heck, I'd be delighted with a $4,000/month pension.... ;)