Based on the information known about Richard Russell there appears to be only one suitable baptism which was to John and Amy Russell in Fakenham in 1778.
Although records may not be complete a FREEREG search in Norfolk found only one marriage for John Russell and Amy.
This establishes her maiden name as Chambers, with a reasonable degree of confidence.
There is only one baptism for Amy Chambers around the right time for her birth which gives her parents as Richard and Frances which are also names of her children.
  

It looks likely that Amy remarried after the death of John.
John seems to have died on 9 Sep 1778 aged 38.
There is a marriage for Amy Russel, widow, in Fakenham on 10 Oct 1792. She would presumably be about 52 years old.

  

Searched Fakenham and all Norfolk via FREEREG but not found any burial for her.
Also searched using FREEREG in case she re-married, but nothing found.

If Amy remarried there is a possible burial for Amy Pitts in Fakenham on 16 Feb 1813 aged 70.
This is consistent with her being baptised in Feb 1742 (that is 1743 in the new dating system.
There is a John Pitts who died in Fakenham 19 January 1813 aged 77.
John was thus born in about 1736.
Whether or not this is the correct Amy it seems likely these are the couple who were married in 1792.