I think you need to post this on the Pasquotank County board rather than the Camden County board. There were a number of Noah McPhersons in Camden County as it was a very popular name, but I haven't seen an Alston. In looking at the 1850 census Alston is in Pasquotank County and owns land.
In looking at Camden County wills there's isn't a Noah in the 1840s or an Alston in 1854. There is however those names and those dates in Pasquotank County wills. I don't know if the McPhersons in the two counties are related or not, but the Camden County McPhersons first settled along the Northwest River in Norfolk County VA and then moved down into Camden and Currituck Counties in NC.
And if he died in 1840 he definitely didn't sign a deed in 1844 - again Noah McPherson is a very common name in NE NC.