Richard, I think you may have got your pedigree wrong. I say this because Lord Farnham inherited the barony of Calderwood as the nearest living  heir-male of the last baronet of Calderwood. The Farnham Maxwells branched off the Calderwood line in the 16th century thus indicating that there are no surviving Calderwood Maxwell lines after the Farnham Maxwells branched out. I would be willing to look at your pedigree and see if I can spot were it might be wrong.