Even though Joe Gargery was more like a father figure to Pip, I don't recall anywhere in the book where it said that he was Pip's "adopted father" as he is described in your summary. Joe married Pip's sister, so that would make Joe Pip's brother-in-law. Pip's sister may have raised Pip and been over 20 years his senior, but she was still his sister, not his adoptive mother.
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I would agree. Joe does not really assert himself as a father figure for Pip at any point. In their earliest and closest times, Pip describes him and Joe in Chapter 2 as being 'fellow suffererers' at the hands of Mrs Joe. They are more partners in the face of adversity. Even as Pip decides he should settle with Biddy and discovers that Joe has already done so shows that their relationship is certainly more filial than paternal.
"Great Expectations" - Charles Dickens