I suspect McIveen should be McIlveen. The 1843 Directory for Belfast lists the following:
McIlveen or McIlvene
James, weaver, 16 Little Donegal St.
David, Soap & Candle maker, 27 Great Edward St.
John, Cloth lapper, 11 Stanley St.
I can find no reference to the name Sneddon and think it likely is a variant of the name, "Snoddon".
There is a Snoddon headstone in the graveyard of the Drumbo Presbyterian Church (outside Belfast).
Erected by Samuel Snoddon, Junior, of Drumbo, to the memory of his beloved and affectonate wife Agnes Snoddon who died July 2nd. 1831 aged 24. Also their infant child Margret who died aged two months. I believe Snoddy and Snoddie are other variants of the name. Other Snoddan/Snowden/Snodden gravestones are found in the Tullynakill Graveyard which is on the west side of Strangford Lough south of Newtownards.