Hi MadManMoon,
Welcome. I hope you find some answers to help you and your son.
My biggest question is where would one find resources for testing children at this age?
You may be able to get testing through your school or you could find a psychologist or diagnostician to give your child an achievement or IQ test. You could ask your school for a professional recommendation, inquire at your local university, or look in the yellow pages.
Which lends itself to the next question of what to do if it is determined that he has an aptitude for learning?
There is an abundance of resources available, many of which are discussed on this site. You may want to look through some of the threads with math titles to get a general idea of some of the more popular math resources.
I am terribly uncomfortable with designating a child as "gifted".
Like you, many of us are uncomfortable with the term gifted. Unfortunately that is the term that was coined to describe a specific segment of the population- individual's in the top 3% of intellectal ability. We cannot seem to find a more appropriate, generally accepted term to describe this segment of the population so we continue to use the term gifted.
The fact is that they [gifted] are simply normal children, no different than their peers.
Though this would make life so much easier, this is not the case with gifted children. That is why so many of us have found our way to this forum. Gifted children are special needs children. The more extreme the giftedness, the more extreme the needs. These needs fall in the areas of academics, social, emotional and even spiritual. As a matter of fact, the needs of many gifted children are so extreme that their families are told by the public schools that the schools cannot meet the children's needs and they must find other ways to educate their children. If your son is as gifted as he appears by the description in your original post you will soon discover, if you have not already, that he does have special needs. Most people who participate in this forum do so to find the resources and support to enable them to meet their children's special needs.