2 How is the GFCF diet supposed to work ?

Lots of other people have explained about this.  The information is readily available on the Internet.  We suggest you go to   http://www.gfcfdiet.com.  They've got a subpage called   EXPLANATION OF DIET

Basically, the theory behind the GFCF diet is that (at least some subsets of) autism is analogous to both celiac disease and phenylketonuria.  All three diseases have to do with incomplete digestion / breaking down of proteins.  Protein fragments that are incompletely broken down, cause damage in the gut and/or in the central nervous system.

*  In celiac disease, the offending protein is barely broken down at all.  The protein fragments that result from the process are fairly big, and therefore stay mostly in the gut, doing severe damage to the gut wall.

*  In phenylketonuria, the offending protein is broken down nearly completely, but the body is unable to handle one of the amino acids, called phenyl alanine.  This is a relatively small molecule, passing easily through the gut wall and into the central nervous system (CNS), where it causes irreparable damage.

*  In the relevant subsets of autism, the protein is broken down half the way. The protein fragments are called peptides.  They are small enough to pass through the gut wall (particularly when this has been damaged to some extent).  They then appear in the bloodstream and the CNS, doing serious damage even there.  Since they don't get broken down in the ordinary way, the body has to get rid of them through the urine.  There are at present three laboratories (one in UK, one in USA and one in Norway) that are capable of doing the analysis necessary to find and identify these peptides in urine samples.

Some of the peptides in question are highly similar to morphine.  They are called gluteomorphine (part of the gluten molecule present in wheat, rye, barley and oats) and caseomorphine (part of the milk protein molecule  caseine). 

The theory behind the GFCF diet is that these two substances (and maybe other ones yet unidentified) are responsible for most of the damage seen in (many) autistic persons.

There are three researchers that have done enormously important work to find this out:  Dr. Karl Ludvig Reichelt (Rikshospitalet, Oslo), Dr. (Sir) Paul Shattock (University of Sunderland) and Dr. Robert Cade (University of Florida).