Unfortunately, there are no MIs for your Duggans.
I would agree with JC as to Thomas being buried 28 Jan 1857 Arbory based on census info.
Margaret was in 1881 living with daughter Margaret Eleanor & her husband John Collister/Callister in Douglas. The Arbory burial register indicates that Margaret buried 18 Sep 1886 Arbory was a resident of Douglas.
1881 Onchan Census
Onchan COLLISTER John 23 Princes St Head O 44 Carter Peel IoM
Onchan COLLISTER Margaret Eleanor 23 Princes St Wife M 40 --- Arbory IoM
Onchan DUGGAN Margaret 23 Princes St --- W 77 --- Arbory IoM

The Margaret Duggan buried Arbory 1854 age 89 was NOT the wife of James--there is an MI for this couple and her husband was William who died 19 Dec 1852 aged 81 yrs Burial record says they lived at Adiery Arbory
Seem to be Wm Duggan and Margaret Quayle
This couple is in 1851 Arbory Census
Ballacubbon
William head mar 79 farmer 22 acres empl 2 labs b Arbory
Margaret wife mar 85 b Arbory
John son mar 46 farm lab & local preacher b Arbory