70# is not too much N
We usually apply 100#
There probably was some N leftover from the corn.
Possibly 50-70# just guessing, maybe 1/3 of the total N
Check your University Wheat Trials,
Plant the varieties that are shorter than average.

Reminds me of the drought of '12
Single digit corn yields,
IIRC, left over N levels of 100-120# acre,
Some growers planted wheat in cornstalks on September 15-20,
2 weeks early, very determined to replace a dead crop with a living crop.
Palisade worked that year.
Those who did not use it had wheat that went flat.

With a zero corn crop, left over N = 50-60%
With a 1/2-2/3 corn crop I would expect 1/2-1/3 of that 50-60% to be left.
So you could have had 40-50 # of N left
With the correct variety of wheat it may have stood ok.