Alot of what you notice sounds familar to me too. My son also cannot look at me when talking. On talking with alot of other mums we have all found that our children find it hard to multi-task for a sensory point of view. So if the child is made to make eye contact they probably won't hear a word you say. But if they listen, or talk whilst not making eye contact they will hear what is being said. When they are watching TV or making a lego model or play with their toy their ears will effectively be turned off. When I have talked to my son about it he says 'just keep calling me name', and that does usually work after about the 5th time.
Some autistic children can associate colour with certain things. Sometimes this can be synesthesia (check spelling!). Sometimes it is just a colour association they have made themselves. Again I notice alot of autistic children can be connections between things that are not 'normal' to us. I don't know if that happens because the experience involved colour for them, or whether attaching a colour to certain things helps them remember or predict what should be done. But it is common. My son went through a period of giving food colours eg. I want to drink the blue milk not the green milk (no idea what that was about). Or "this tasts very very yellow". But he hasn't done that for a long time now.
At nursery my son wouldn't join the other children to do activities or to play. He would take things off the other children or break their models, puzzles etc. But if a child even went near to his stuff he would get angry/defensive or disolve into tears.
He went through a phases of head banging, vomiting, scratching his face, hitting himself in the face. All that has thankfully past. At the moment he has got a thing of licking his bottom lip and all his chin is red and sore.
It is very interesting that you say he talks in a monotone and the fact that he almost 'talks to you' giving you a statement of facts. That is what my son did as well. He didn't ask questions or seem curious about things. He seemed to soak up information on things he was interested in and would then reguritate all this information. Sometimes I would trigger it by mentioning something eg. "can you see that spideer?", and he would reply "yes, spider crabs are from the .... ocean they have ... legs", and give me an overview of spider crabs. I would ask him "where did you learn that?" and he would seem genuinely surprised that he knew that information and say "I don't know". He also has an american accent (we live in the UK!) as well as a sing song style and a strange intonation. All these speech patterns are indicative of being on the spectrum.
You say your son talks loudly (very common), and the fact that he doesn't have theory of mind to understand his brother is asleep and if he talks loudly he will wake him up, also shows some difficulty in predicting outcomes.
I would bring up your concerns with your paediatrician. All of what you have posted should be ringing bells. Also read through the clinical criteria as a child needs to have a certain amount of difficulty in all the areas for them to get a diagnosis.
From what you describe, it does sound like some form of autism spectrum disorder. Whether it is aspergers I don't know. Aspergers has no language delay. If there is language delay, then likely he'd get the PDDNOS tag.
I'm sorry to hear about what else is going on. Hopefully that will get resolved. I'm sure it must be hard on both of your sons as well.
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As far as the blank stare goes, don't assume he's not deep in thought. Being autistic myself, I sometimes, (more in the past) get people asking me "What's wrong?" "Are you sad?" When all I was doing was just observing things around me or pondering over stuff in my head.
I get in a couple modes with the blank expression:
Observation mode: I'm focused on what is going around me or an object that catches my attention. It may be something large like a person or something tiny like a fly buzzing around a distant window. This seems to be how I can "record" things to be recalled in my memory at a later date. I can remember the most detail if allowed to stare. During that sometimes I can remember what people are speaking about around me or saying to me.
My facial expression is a lesser priority. It takes conscious thought to make an expression. (doesn't come automatically) and because of that, it takes concentration away from what I am observing.
Contemplative mode: I'm focusing inward on my thoughts. While I'm focused on my thought, I can't focus as much on the outside world. I can do simple repetitive tasks during that time, but complex tasks will take away from my mental concentration and ability to do complex thoughts.
Listening to people speak fits into this mode. The more I am trying to concentrate and "record" the person speaking, the less attention I can pay to my face and expressions.
Here's a great example of this going on:
http://detailedthinker.blogspot.com/
(my blog)
I'm performing a rather simple repetitive and rather automatic task, which is grabbing foxgloves and cutting them up to be used as mulch. Later on I was picking flowers off the azalea bushes.
Likely my facial expression was rather blank, because once again that isn't my focus.
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With maturity and skill I become able to switch between the two modes at a quicker rate. That way I can still be lost in thought but yet be able to "switch off" so I can cross a street without getting hit by cars.
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Whispering:
I can relate... Either I talk loud or I whisper... Talking softly took me a lot of practice and I still struggle with it, because I feel tension in my vocal cords when I speak softer. Also when I am into speaking mode, I am concentrating on what I am about to say more than my voice.
To me speaking is a lot like writing. The rough draft is all choppy and if I can control it, that draft stays in my head...Ideally, I like to think out several possible outcomes in a conversation before I speak to the person and rehearse my speech in my head.
That way hopefully by the time I can speak it, I won't stutter or say something awkward. If I don't get the chance to rehearse in my head or I am anxious, then I am prone to stutter, stammer, and forget what I am about to say in mid sentence. Paying attention to voice and tone, as well as facial expressions once again goes to the back burner.
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Lack of reciprocity or turn taking: Short, quick sentences don't give me enough time to plan out what I am saying.
This “planning” can take a long time to nearly a split second. With maturity hopefully this mind to speech turnover happens quicker.
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I hope some of this helps, and I hope things get better. You may want to try talking with your son to see how he feels about the whole family issue. I'm sure he is feeling something even if he may not show it on his face.