I have found an Australian website which suggests that:
(i) Murdoch was the son of William and Henny MacLeod (both born c. 1770); and
(ii) He married Catherine MacLeod from (or in) Bracadale in 1811.
Does this information agree with your data? When I have tried searching for the marriage, I've found more than one possibility:
(a) Marriage to Catherine Graham in Barvas in 1816
(b) Marriage to Catherine Urquhart in Cromarty in 1819 (Not so likely as this Murdoch was a sailor.)
Like you, still looking for the death of Murdoch & Catherine's son, Murdoch (Junior). Been searching the on-line information on gravestones (which I'm sure you have done, but I hadn't looked there before.)
Best wishes, Kevin