difficulty with expressive language

I know an individual who has difficulties in two areas: expressive language and executive functions. For expressive language he has a lot of difficulty answering open-ended questions (orally). For instance, if you ask him how his day was, he might say something like "I really like to play this computer game." He seems to be unable to pick out the pertinent parts of information and/or just skips over one thought of the process. This comes out a lot in his writing. We're in college, and I proofread his writing for him, and a lot of the time it makes no sense... he tends to just repeat the question 5000 times instead of actually answering it! However, he is able to explain to me what he meant to write - and it makes perfect sense. He is ADD and also does not get many social cues (he doesn't know that if he is spoken to in a whisper, for instance, that he is supposed to RESPOND in a whisper, oftentimes he'll just yell right back to you!) and is also very literal.

I'm assumming this guy has some kind of LD but I'm not sure exactly what it could be! Any ideas? Any suggestions on how to help him communicate better? (He's very frustrated!)

-Grace