Thanks for your message.
You have obviously done a lot of work on your family history already!
Unfortunately, the reality of finding documentation pertaining to births/baptisms/marriages/deaths in Ireland prior to 1800 ? particularly in rural areas ? is that they simply may not exist. Some registers for urban areas pre-dating 1800 may exist ? though often these can be fragmented- as there was an increased need in cities or larger towns to document the population. Please also note that the Church of Ireland was the official church of the country and therefore the bulk of information that does survive for earlier periods is often from these registers.
In order to determine which registers are relevant to your search, it is important to try and establish where in Antrim Samuel and Margerat came from. Do you have any documentation that mentions any townland/parish/village/towns?
Some websites which may help in your search are:
The National Archives of Ireland http://www.nationalarchives.ie/genealogy1/genealogy-records/introduction/
The National Library of Ireland http://www.nli.ie/en/family-history-introduction.aspx
The National Archives UK ? genealogy search: http://www.nationalarchives.gov.uk/records/looking-for-person/
The Public Records Office of Northern Ireland http://www.proni.gov.uk/index/family_history.htm
Alternatively you could try contacting the Ulster Historical Foundation-however a fee may apply for their services. Here are their contact details:
Ulster Historical Society,
49 Malone Road,
Belfast BT9 6RY,
Phone: +44(0) 28 9066 1988 Email: email@example.com
I hope that this helps. Remember to post any new inforamtion that you come across as the more more information you post, the more likely it is that one of our volunteers will be able to advise or assist you. Also include information concerning which sources you may have already used so others may further your search.