Although it all sounds REALLY annoying... (ugh, boogers!) I don't know that there is cause to be overly concerned. Just keep an eye as he grows to see if things are getting better.
I would also wonder if the snot is caused by a food sensitivity. Does he eat a lot of dairy? Too much dairy can cause excess mucus.
I wouldn't stress at all about number and letter recognition right now. My second son was like that. He could say all the words, but if you asked him about something, it was like he just didn't care. (Everything was "blue" if you asked him what color stuff was)
As for the walking; is he pigeon toed at all? Does he sit in the "W" position often? Some kids are simply not as co-ordinated. I used to care for a 3 year old that would trip over a shadow, I swear. It was frustrating, but he just had to "grow into himself".
There is a disorder that involves a child never feeling full, and therefore eating until they are sick. I would certainly keep an eye on it, but again, if it was that there would be some more really severe signs.
Good luck!