McLaughlin/Cash from Banagher, Ferbane, Rahan

I have received some wonderful help in the past here, so I am updating and asking a few questions.

James McLaughlin & Julia Cash married 1826 in Banagher.  *I have originals for all records except where noted.

Children:

Mary & Catherine (twins) born in Ferbane,  April 1828.  (Mary died young - no record.)

Andrew born in Rahan, 1832

Mary born around 1834 (no baptism record)

John born in Rahan, 1836

James born in Rahan, 1838

Four other children were born to James McLaughlin & Julia Cash in Banagher.  Other than their birth, there is NO record of them again.  They did not emigrate to America with the rest of the family.

Bridgid, 1840

Ann, 1842

Julia, 1844

Joseph, 1845

In 1848, oldest daughter Catherine arrived in America and married the following year.  No record for her father's arrival, but he likely arrived before her or with her.  

1848 Andrew McLaughlin (age 16 murdered in Wood of Glynn, near Ferbane.  He had recently been given a job that displaced another man.  His mother reported that Andrew's position was "wood-ranger of Glyn and caretaker to James F. Armstrong, Esq. of Balliver."  The man whose job had been lost, and his friends ambushed Andrew and killed him (see separate post on this).
This makes me think that this family had jobs that explained their moves from Banagher to Ferbane to Rahan, back to Banagher.

1852 Julia Cash McLaughlin and children Mary, John, and James arrive in Boston.  No sign of Bridgid, Ann, Julia, Joseph.  Julia lists the three children with her as several years younger than they would be.  

I can track the family from this point on in Massachusetts.

QUESTIONS:

1)  Am I correct in assuming that the four children born 1840-1845 are also children of the same James McLaughlin and Julia Cash and likely died in Ireland?  I'm basing this on the fact that the family lived in this general area, Cash (and Julia) are not overly common names, and I can find no other marriages for a couple with these names.  I can find no death records for these four children (very few of course) nor can I find a marriage for any of them using civil records.)  I don't believe that after losing a son so tragically, Julia would willingly leave them behind.

2)  Any ideas for the kind of job James McLaughlin may have had that involved moving around this area?  Might he have worked for James Armstrong as well?  Would that give him connections to see that his 16 year old son secured what would appear to be a pretty impressive job for a 16 year old.

Any thoughts or direction very much appreciated!  

Best regards - Ann