If I’ve understood correctly, there are two separate issues here, (1) place of burial and (2) possible Jewish origins, and these have become confused.
(1) Manor Park was not a Jewish cemetery. So the burial of your people there does not support the theory that anyone in the family was Jewish. Jews who died in London at this period had a large choice of consecrated Jewish cemeteries to go to. They are unlikely to have chosen Manor Park.
As was mentioned in your other thread, it was very common for people from Southwark/Bermondsey to be buried in east London cemeteries. Even though some of the family were buried at Camberwell and Nunhead, unless these were private family graves, there would be no reason to expect everyone in the family to be buried there, especially when the family was large and there were many infant deaths. As well as pressure on burial space, cost may have been a factor – Manor Park was a newer cemetery than Camberwell, with more space available, and might have been offering a better deal at the relevant time.
(2) On the matter of your grandmother, Sarah Forrest born 1886, Jewish heritage passes down the maternal line, not the paternal line. So if you believe Sarah was Jewish, it is her mother Charlotte Capel/Cable who should be investigated, not her father William James Forrest aka Goodman. In any case, according to your information above, William James Forrest born 1862 was illegitimate, born 4 years before his mother Susan Forrest married William Goodman, so his blood-line may not have been Goodman at all. Even if it was, the surname Goodman has origins in England going back to medieval times. It is of course true that some Jewish families also have that name -- many of them will have anglicised it from a European surname.
From the information you’ve posted above, with all those Anglican baptisms, marriages and burials, it is hard to see any evidence of Jewish heritage in this family as things stand. But if you still want to pursue it you might want to focus instead on Charlotte Capel/Cable.
Have you already posted elsewhere asking for help with Charlotte’s origins? If so, please post a link to the earlier thread.