What other scientifically viable theories are there that contradict Evo.
Well, there have been several. For instance, Lamarkianism, or Lysenkoism. The fact that you have never heard of them is a testament to the degree to which evolution is better than all the other competing theories. It's simply the best explanation for the history of life on Earth that we have, and, to date, nobody has come up with a better one. But maybe somebody will. Maybe you will.
But that doesn't change the fact that the chances of a mutation having a beneficial effect are extremely low.
Yes, that's true. But every organism is basically guaranteed to have somewhere between 5 and 50 mutations (that's a very rough, imprecise ballpark estimate). So, per generation, that's millions of mutations, several (say, less than 10) of which will probably be beneficial.
You're right that a beneficial mutation isn't likely. But there are so many muations per new generation that benefical mutations are a certainty.