Edit:  Wait, I think you're making this more complicated than it needs to be.  If he had no distributions, why are you trying to report the value of his IRAs on an 8606?

From Pub 590B (page 14, about 1/3 of the way down the second column):

https://www.irs.gov/pub/irs-pdf/p590b.pdf

Note. When figuring the nontaxable and taxable amounts of distributions made prior to death in the year the IRA account owner dies, the value of all traditional (including SEP) and SIMPLE IRAs should be figured as of the date of death instead of December 31.

Rick