I suspect your wheat will survive this forecasted cold snap.  Wheat is resilient.  Said to have 9 lives.

But if you decide to plant it to corn.... the fertilizer you applied to the wheat will likely be of equal value for a corn crop.  

It's also possible applying manure now on the wheat crop, won't adversely affect the wheat crop.  As long as no compaction is caused, and the manure doesn't smother the wheat.... good chance the wheat will benefit from the manure.



Good luck with your decision,

gordon