1.Regarding the birthdates & places for William H. (April 1768), Sarah (15 Sept 1780) and Mary (probably by 1782):
-In 1780, New Brunswick did not exist.It was created in 1784 from a part of Nova Scotia.Any records prior to 1784 would refer to Nova Scotia as the place of birth.
-If Sarah was born in Canada in 1780, that was before the Loyalist exodus and implies that her parents were there as British settlers after the French and Indian War or that they went to get away from the anti-Loyalist persecution during the War.If they were Quakers, maybe they went to get away from being forced to take a side, etc.
-Clark's information would have come from the land petitions and the land grants at the Provincial Archives of NB so that means William Harrison must not have identified himself with a regiment in his peitions.Land in New Brunswick was granted to regimental groups at first.Since William went with the Quakers, he is identified with them.He answered the muster roll for the 74th Regiment, but I don't know if that means anything.It was so isolated in Beaver Harbour, and provisions so critical, that answering "a" call for a muster roll was imperative.Looking at the other names on the petitions William Harrison filed might be insightful.
-Birth records in 1780 are unlikely.Baptismal records are your only hope.What British settlements existed in "Nova Scotia" in 1780 is the question.Having a bible record is very impressive - and I belive very trustworthy.
2.Almost all of the Quakers who settled in Pennfield were from New Jersey or Pennsylvania.William Harrison is not listed on any New Jersey regiment muster rolls - but that doesn't mean he wasn't in one.It simply means those muster rolls have not survived or have not surfaced.He was very likely in several different regiments during the course of the war.And, regiments were absorbed into other regiments, and names changed.I suspect Stephen Sands was in the Loyal American Regiment or the Prince of Wales American Regiment at first and his regiment was absorbed into the Queen's Rangers.Stephen listed his service as 7 years in the Queen's Rangers but he doesn't show up on a QR muster roll until 1780.Stephen's regiment would only have been known as the Queen's Rangers after the war.Stephen was disbanded as a Queen's Ranger in "Nova Scotia" in October 1783; he mentioned this in his first land petition.(The Queen's Rangers were first Roberts Rangers, etc.)
3.Families didn't all go with the Loyalist dad.Maybe mom didn't want to go, or couldn't for health reasons, or was going to go later if she had little children.Maybe the Loyalist was going to go and check it out and then go get his family.This would mean that mom and kids had relatives to stay with; a safe place from Loyalist persecution.Many Loyalists went to Canada and then turned around and went back to the US.
I'm guessing the Harrisons were in Canada after the French and Indian War.
Some Sands went to Pennsylvania, like #27, John Sands.#111, David Sands, was a Quaker preacher.
There was an association that petitoned for land in Canada, I think it was the Cape Ann Association.One of the men involved was a Thorne; it was preLoyalist - about 1780.