1. Who is Peter L Rickman?
Only more research can answer that question. The fact that both Peter and John Rickman married GOINs in the same area, and around the same time, is something worth noting.
Rickmans appeared to like the given names John, Peter, William, and Thomas.
For now, it just serves as a reminder that there were Rickmans / Hickmans and GOWENs/GOINs among the early free people of VA/NC.
2. What was Mariah's maiden name?
You will have to do more research on Mariah. Was "Bridgeman" an actual surname in the area at the time? Could it have been a surname somewhere in her ancestry? OR was the informant, somehow, mis-informed? Who was he? Could he have known first hand?
3. Learn the lay of the land (in my original rsp).
You are now in NC/VA in the mid 1800's. What records are available?
Where (township/County/State)? and When (time period)?
4. In addition, learn what unique records may exist for Free 'African Americans' pre-1860. Are there existing "Free" Registrations for the area in which your ancestors lived?
Paul Heinegg sets the early framework. However, you will have to do research to bridge the gap between where his work ends, and when/where your earliest identified relative is found.
The good news: That is only one or two generations.
The challenge: Finding the records to tie YOUR Rickmans of 1860 to earlier known (documented) generations of Rickmans in NC/VA.