Quote1) Epicurus' own words take precedence over all other source material. Anywhere Epicurus leaves room for different interpretations is not narrowed down by commentary from other sources, such as Philodemus or DeWitt. Neither will individual quotes be taken out of context with his whole body of work.
I just read this a little closer and need to convey concerns about Philodemus and Dewitt being mentioned as examples of "other sources."
I firmly agree that Epicurus's extant works take precedence. No question. It's hard to know what Epicurus wrote if it is quoted in a hostile source like a rival pagan writer or early Christian, but the Letters and Herculaneum scrolls that survive are number one.
However, I would consider Philodemus as a primary source of classical Epicureanism with his direct links to the Garden in Athens. I would place Philodemus higher as a reliable source than Cicero certainly. Cicero is helpful, but he had an agenda to write his version of Epicurean doctrine and then contest against it. Philodemus had an agenda but it was transmitting and documenting Epicurus's philosophy to the best of his ability and understanding. And again, Philodemus was a student of Zeno of Sidon who was the successor of Epicurus in Athens.
All the modern academics and commentators - Dewitt included - are looking through a glass darkly and are definitely secondary sources. I understand we have to rely on their scholarship and translations, but I would not include Philodemus among them as just an "other source."