P.M.
Wow, O., you have actually knocked my breath out with your request. I'm not trying to be unkind, just make an honest observation. I had to read it carefully twice just to figure out what you are asking.
If your life around your son is as fast, frantic, and jumbled, I'm guessing your son may have a combination of problems; speech delays, some sort of hyperactive disorder, sensory integration issues, to name just a few. And some of his challenges may be hereditary. That creates difficulty for him, sure. But every child has challenges of one sort or another to overcome, and that's just the nature of human life.
May I suggest you learn to slow down and pace your speech when speaking to your son. Work on organizing your thoughts into clear ideas. Try to keep your voice soft most of the time when answering his questions, so that he'll have to focus more carefully on your answers.
Read him lots of books appropriate to his age level. This may help his communication difficulties. Build his vocabulary a little at a time. Knowing his alphabet when he starts school is nowhere near as important as understanding a large vocabulary.
And recent studies show that preschool children don't benefit much from drilling on academic skills. What they need is play, lots of it. It's their job. They'll exercise their imaginations and physical capabilities, interact with others, learn to solve problems. All these things will help make them better students. Kids who are pushed to learn academics may start out a little bit ahead, but by 4th grade those abilities have leveled out. And those same kids might have lost the thrill of learning if too much is forced on them before they are ready. You don't say how old your son is, but he doesn't seem ready for the alphabet yet.
If you disagree with your pediatrician about waiting to get your son tested, you might see if you can find a different doctor.