More haste, less speed! I noticed as soon as I pressed send that I had been too hasty! It was the name of Donald's wife (Angus's mother) that the informant didn't know and Angus's wife Jane (/Jean) WAS at home in the 1841 Census returns. In my haste I overlooked the fact that she was indeed present, but recorded under her maiden surname (McIntosh). Duh! Interestingly, there was also a John McIntosh present aged 20 [i.e., within the age range 20-24 - ages of those aged 15 and over were rounded down in the 1841 Census returns], who might well be a brother of Jane or a cousin (or indeed not related at all!). Unfortunately, relationships were not given in the 1841 Census returns.
Angus's stated age (35 [i.e., 35-39]) in the 1841 returns doesn't exactly fit with his stated age ("60") at death (35-39 plus 15 years (1841 plus 15 > 1856) gives anywhere from 50 to 54 as possible in 1856, but as I said, perhaps the informant didn't really know Angus's age ... Jane was "25" [i.e., 25-29] in these returns. Always remember, however, that people didn't always know their own age back then (never mind anyone else's) so if you add in all these uncertainties, the link to that Angus may well be correct, otherwise just ignore all of this, except for the answer to your original question, which was "Donald"!
And, before I post this off ....
... it is interesting that you link Angus to Perth, given that he died in Glasgow (60 Tobago Street, Glasgow) and McLucas is an Argyll name? I see that he is still in Glasgow in 1851 (aged "52") at 116 Garscube Road and with place of birth given as the parish of Kilninian in Argyll (with wife Jane, 42, daughter Jessie (i.e., Janet), 15, and another daughter Margaret, 8. The children were born in Glasgow, but his wife states Killin, Perthshire as her place of birth.
That looks better, as 52 in 1851 would give ca. 57 in 1856, which is close enough to fit the "60" as his age at death ...