One psychological theory about ASD is the "Intense World Theory" (IWT): http://journal.frontiersin.org/Journal/10.3389/fnhum.2010.00224/abstract
The rough idea in IWT is that ASD brains process related information more intensely: it gives us great attention to detail, for example, but we are easily overloaded by stimulation that most (NT) people find "just right" but we (ASD people) find "too much".
The Theory claims that it can tie together all the aspects of ASD that you mention:
- social/communication/epathy: faces etc are too intense so we avoid them. In fact, we find people in general require just too much intense processing - we are overstimulated, burnt out, by interactions that the average NT would not find too intense. As people and social interaction are one of the major stimulants for the (NT) human brain, they are guaranteed to be too stimulating for the ASD brain.
- interests: our attention to detail, our aversion to change, and our brains geared for technical thinking rather than social thinking mean that we specialise in (fall in love with) specific topics where the specific details keep our brain interested, while the general familiarity stops us from being overwhelmed by too much novelty. Special interests help us to (hyper)focus on one thing - meaning that we get to filter out everything else and ignore it ... thereby reducing the load on our intensely processing brains while keeping them interested in something.
- aversion to change: new things require a lot more processing than familiar things (for people in general, not just ASDies). IWT predicts that ASD brains would find new experiences overwhelming because there is so much to process, and the ASD brain tries to process it all intensely, causing overload. So the ASD person seeks out the familiar in order to reduce this too intense processing.
- sensory processing: we process sensory inputs intensely, so that the world seems too loud, too bright, etc. IWT woud definitely predict strong sensory sensitivity for people with ASD.
IWT is one of the more interesting psychological accounts of ASD, IMHO. I am not an expert in it, but Henry Markram - the guy who puts IWT forward - is a leading neuroscientist in Europe. One of his research projects has been given a massive grant to model the human brain, so he is not a minor figure in the neuroscience world. He also has a son with ASD, which got him interested in researching the topic.