Hello Jim,
A boy by the name of Pehr Månsson was born on August 4, 1730 at Webbantorp in the parish of Grebo (AD Online: Grebo C:2, p 429). If the date of birth you have is correct, he is most probably identical to your Petrus Mansson.
His parents were Måns Pehrsson and his wife Margareta Olofsdotter. Måns i Webantorp died on September 6, 1760, and his age was then stated as 69 years and 4 months (AD Online: Grebo C:2, p 533), suggesting he was born in the spring of 1691. Unfortunately, the parish birth records are available only from 1694.
When Måns and Margareta married on October 14, 1722 (AD Online: Grebo C:2, p 281), they lived at Sarpebo. By the way, Margareta's father may perhaps be Olof Svensson in Sarpebo, mentioned by Magnus Arnér in an earlier message on Anbytarforum: . Anyway, the newlyweds moved to Webbantorp, where their first child, Swen, was born on December 12, 1723.
As there are no records of catechetical meetings available until 1795, I have tried following Pehr and Måns in the schedules of population. Apparently Måns took over as farmer at Webbantorp, when his father died in 1760. On January 6, 1773 Pehr married a widow from Norrby by the name of Lena Sophia Christ:sdotter (later, when their son Magnus was born, she was named Adamsdotter - I haven't tried to check which of these patronymics is the correct one). As Magnus was born in Norrby, Pehr probably moved there from Webbantorp, when they married. And in the schedule of population for 1786, the residents of one farm in Norrby are Pehr Månsson och hustru. In 1787 they have moved from Norrby to Björntorp, where Pehr dies on June 7, 1791 (AD Online: Grebo C:2, p 539). Somewhere along the line Lena Sophia has died too, because in 1795 the name of Pehr's widow is Maria (AD Online: Grebo AI:1, p 43).
On January 23, 1798 Magnus Pehrsson marries the maid Maria Beata Beckvall from Föltorp (AD Online: Grebo C:2, p 347). But this you probably knew already.
Best regards,
Hans Olof