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Subject:  How closely should US (MD 1776) and German (Zillhausen bef. 1749) records typically match for the same family?  What European records might I find?

I’m trying to trace a family that immigrated from "Germany" to the "USA" in 1749 through Philadelphia, PA.  The conventional wisdom provides three sets of records to match.
1)   The German birth records.
2)   The Immigration record (less detailed).
3)   The Maryland Colonial Census of 1776, which included names and ages for all residents.

Here is a summary of the records for the five immigrants and how they are similar or changed going from source 1 to source 3.
A)   Johann Martin Herre (b. 1720, Zillhausen) > Hanss Martin Herre > Martin Herry (1720)
B)   Anna Maria Seßler (b. 1720, Zillhausen) > Anna Maria Sassler Herre > Mary Herry (1730)
C)   Jonathan Herre (b. 1742, Zillhausen) > 1 of 3 unnamed children > Jonathan Herry (1745)
D)   Simon David Herre (b. 1744, Zillhausen) > 1 of 3 unnamed children > David Herry (1750)
E)   Johan Herre (b. 1748, Zillhausen) > 1 of 3 unnamed children > Martin Herry (1748) called “Martin Jr.” in many records, so he was a "John".  [There was also a John Herry b. 1760 per the 1776 census, thought to be Martin's brother.]

Of interest:  There is also a report of “Hans Herre” returning to his home in abt. 1765 to claim his share of an estate (100 florins; roughly $2000 today), before returning to Pennsylvania.  There were legal records of claims (tax?) due on the estate.  (Source:  New World Immigrants, Vol. II, on Ancestry.com.  I think this is from a book by Michael Tepper, 1980 citing “Einige Amerika-Auswanderer des 18.  Jahrhundrets aus Wuerttemberg.” [“Some 18th century emigrants from Wuerttemberg to America.”] In Suedwestdeusche Blaettr fuer Familien und Wappen-kunde.  [Southwest German leaflet for families and heraldry customers.]  Stuttgart, February 1957, Series 9, No. 1, p. 442.  Editor Reinhold Scholl, Stuttgart-Sillenbuch).

More specifics of individual records on request.

Questions primarily for US researchers:
a)   Is this a reasonably good match for Maryland about 1776, despite the name and age differences? 
b)   I gather there would not be a record of Johan Martin Herre’s return trip to Europe around 1765, since he had already signed a loyalty oath?

Questions primarily for EU researchers:
c)   What’s the best way to find records of this family if they stayed in Germany (or Europe) rather than immigrating to the US in 1749.
d)   Would there by European records of the estate?  Or the return trip?  How would I find those to see if they involved Zillhausen or this Johann Martin Herre (b. 1720)?

Thank you!
George C. Moore
Likely 5x great grandson of Johann Martin Herre (b. 1720)