There are 8 pages of Thomas Hall's in the 1861 index, a lot more information would be needed to locate him - the birth certificate of James would provide an address.
There are 3 pages of George King's in the 1861 index aged 15 +/- 5 and none appear with possible father John.
There are 2 Martha Salisbury's - piece 112 folio 110 & piece 59 page 18.
RG9/112 folio 110:
2 Middlesex Court, Pancras
Jake (or John) Salisbury, Head, 6(?), Sewer Man, Herts, Offornsheet(?)
Mary Salisbury, Wife, 43, Buckchard(?), Hambleton
Thomas Salisbury, Son, 16, General Porter, Middx, London
Mary A Salisbury, Daur, 14, Flower Maker, Middx, London
Martha Salisbury, Daur, 13, General Servant, Middx, London
Edward Evans, Nurse Child, 2, Middx, London
There is no Middlesex Passage listed in the Pancras Street Index, so it's likely that Middlesex Court became Middlesex Passage. The Enumeration District is described as: "All that part of the Parish of Pancras comprising Chapel Street, Clarkes Place, The Grove, Seamans Place, Julers(?) Buildings, Dears Place, Dentons Buildings, Middlesex Place and Court".
There were no King's living at 11 York Buildings in 1861.
Hope this helps
Linda