I agree with ASU meaning Acting Sergeant Unpaid.
I think that all the variants of Supy mean Supernumerary, ie a temporary administrative attachment to a unit rather than a proper posting to it. In this case, other than his one day at 2 ARC Rabat/Sale, it seems to occur after he is posted missing and until he is presumed dead. Supig rings no bells with me. These are hand written entries by Admin Clerks, no doubt with their own idiosyncratic ideas about spelling and abbreviations.
As to "on c/a to 311 Ferry Training Unit", how about Course Attachment?
Interesting that commissioning from the ranks means leaving and then re-joining the RAF. You learn something every day! Thanks LR.
ACDW is the Air Crew Disposal Wing, Brighton
http://www.raf-lichfield.co.uk/GroundUnits.htm