I haven't got a Samuel occ shoemaker - Samuel's father, John (m Sophia Short), was a shoemaker and Samuel's daughter, Sophia (m John Daniels) was a shoe binder.
Frances definitely had family in Leamington Hastings. You may be right in that she returned there due to illness or maybe her family had her taken back there to be buried after she died. I didn't find a burial in Marton or Wappenbury in the time frame.
The RO is closed next week, but I'll have another look for Frances' burial when they open and also the marriages of Sophia and Isaac to see what they gave as their father's occupation.
Interesting thought that Betty may have been the one who wasn't free to marry, although I'm not sure why as (I'm pretty sure that) she hadn't married before. And I too suspect that Samuel was the father of Martin. That said "Martin Nathan" was a family name in the Knight family - Betty had an uncle called Martin Nathan and another uncle of hers, Peter, called one of his son's Martin Nathan.