DLA Assessment

Please bare with me as I am new to this group though in the few threads I have read it appears very helpful and supportive.
I have applied for DLA and following the ATOS home assessment I was awarded the lower care rate and declined Mobility. I have now appealed and await a Tribunal date.
My query is in relation to the Atos Dr's report.

1) In his report he states that I walked 8 metres plus in my living room which is rather laughable. Is the Dr allowed to ask me to walk as part of the examination as I seem to remember reading somewhere that they could not ask you to walk as part of the assessment.
2) In the section where the ATOS Dr relies on a numeric score system re upper and lower limbs there appear to be entries that may have slightly favoured me that the Dr has scribbled out and written over the top of them in order to totally obscure them. Is anyone aware of any guidelines that the ATOS Dr's have re correcting errors i.e. are they required to ensure the original entry is legible with simply a line thru it and the amended entry next to it and initialled.
3) Would anyone know what information is provided to the ATOS Dr's before they complete the assessment i.e. are they provided with my GP's and consultants notes? The ATOS Dr makes no reference whatsoever to the arthritis in my left foot but does mention the joint replacement in my right foot and issues with my back etc.
4) If I have issues with the report to whom do I complain, DWP, ATOS or GMC.

If anyone can help I would greatly appreciate it. Cant get help from Brentwood CAB or any other Support Agency.