First off, what you are discribing is not dyslexia. Dyslexia is the inablity to understand, decode, and manipulate phonemes, at the most basic level. This effects spelling and reading for most dyslexic children. In order for your sone to have an issue, he would have to be beyond the developmental level that it would no longer be typcial for him to make order subsistutions, reversals, and transpositions, and he is not nearly there yet. So, short story, way too soon to worry, long story, if this continues, it may be a processing issue, but not necessarily dyslexia.
Actually, that he can identify the phonemes c a and t and identify the sound symbol relationships that go with them, and has a strong ordered memory for one through ten are good skills.
One thing all parents should know is that there is an order to how kids learn things, and all children have relative streanths and weaknesses that are all within the typical range, but sometimes one skill is more advanced than another (like recall or sound symbol phoneme identification) while another skill, like sytanx, sequence, or visual perceptial or visual foreground (seeing the word as one group in order) is less strong, but not out of the normal range for his age, and that will present as minor glitches as he learns. It is generally nothing to worry about. It makes for an uneaven learning profile, and just about every child experiences this to some degree.
M.