Abraham's surname is spelled various ways - CLEMENS, CLEMENZ, CLEMENCE in records.
In Berks Co Births,1710-1780, by John T Humphrey, pub 1997, page 51:
Trinity Lutheran Church, Reading, a dau. baptized named Margaretha Barbara CLEMENZ born 7/9/1779; parents Abraham and Christina CLEMENZ.
I believe this is Margaret who m Daniel Vanderslice.
I do not find an Elizabeth as a dau of Abraham and Christina. There were other children born to them, but none named Elizabeth are listed in Humphrey's Births or in the 4 vol set of Berks Co Church Records of the 18th Century by F Edward Wright.And Elizabeth would have to have been born early in 1770s, if she married John FUCHS in 1790.That leaves a big gap between her and Margaret b 1779.
In the 1784 tax list for Berks Co, Abraham 'CLEMENCE'was shown in Reading with 5 people in his household.No land, house or animals.He must have been renting.This would be 3 children plus the parents, so there must be more children that we don't know.I am not sure when the tax list was prepared, but I would doubt that a child born in 1784 would have been counted.
The other children of Abraham and Christina that are shown in Humphrey's book are: Christina CLEMENS b 10/9/1781 bapt 5/19/1782, by Rev. Boos in Schwartzwald Reformed records, spons: Sebastian Ries and wife Dorothea Maria Esther CLEMENZ b 2/6/1784 bapt Trin Luth church Johann Michael CLEMENZ b 10/1/1786same Sara CLEMENZ b 10/23/1788same Barbara CLEMENZ b 2/4/1791same Abraham CLEMENZ 4/30/1793same
Maybe dau Elizabeth was baptized in another county?I checked Montgomery Co, but no Elizabeth is shown there.
Another puzzle! Am glad you have the Pennypacker notes.