Yes, there is residual sugar, but it's complex sugars that not even yeast that specializes in fermenting sugar can consume. Plus there is alpha acids from hops, as you point out, there is alcohol, pH is low, oxygen is gone, there's a CO2 blanket, etc. So it's a very, very difficult environment for microorganisms. Pretty close to none that cause disease can grow in this environment.
Is it more than 99.99999999999999% safe? No. Is it vastly safer that water? Yes.
Is it more than 99.99999999999999% safe? No. Is it vastly safer that water? Yes.