Will Ammonia react with Gasoline mixed with Ethanol?
A fuel that is mostly ammonia is an altogether different fuel formulation that would not reap the benefits of the oxygenated fuels program in the US for gasoline. In other words, there would be no reason to mix in ethanol or any of the other approved oxygenated species used in gasoline (the specification requires 1.5% - 3.5% oxygen by weight during the winter (state dependent) and is reported as ethanol, regardless of the oxygenated species actually used).  

According to this US Environmental Protection Agency document:  


  Oxygenates are fuel additives that contain oxygen, usually in the form of alcohol or ether. Oxygenates can enhance fuel combustion and thereby reduce exhaust emissions. Some oxygenates also boost gasoline octane. The Clean Air Act requires use of oxygenated gasoline in areas where winter time carbon monoxide levels exceed federal air quality standards. Without oxygenated gasoline, carbon monoxide emissions from gasoline-fueled vehicles tend to increase in cold weather. Winter oxygenated gasoline programs are implemented by the states.  


The octane levels of ammonia fuels are already very high at around 120. There would seem to be little benefit in the form of carbon monoxide emission reductions by adding oxygenated hydrocarbons to a fuel that is 70% ammonia.  

So, the bottom line is that there is no reason to expect ethanol and ammonia to be in the same fuel formulation. Furthermore, if there were ethanol in the ammonia based fuel, there is no reason to expect the two to react in any significant way.