Does anyone have experience working with secondary qualitative data for their PhD or elsewhere?

Struggling a bit with questions of reflexivity, justification and especially with methodological and analytical aspects. Largely because I am (unfortunately, I feel) expected to use this data for my PhD and, well, I just don't feel that it's very easy to work with (the research proposal for which I was awarded funding for the PhD was completely different, mixed qualitative/quantitative approach, but after realising this will be impossible given the data here I am...again, I have no choice but have to use this data as part of the conditions of my scholarship - one panel reviewer has even suggested scrapping it and doing something else, although it's a bit late).

It's my supervisor's old data from longitudinal interviews (there's a lot of data and quite a big sample). For ages I couldn't access a lot of it as it was confidential and locked away, and much of it in old formats like mini-cassettes etc. To date he hasn't been able to tell me anything about his thinking behind design, methods or much else regarding his conducting the interviews or this project, usually changing the topic or making vague suggestions. Now having done the legwork of transcriptions, some coding in NVivo etc., the data just isn't very good and again I don't know what the thinking was behind it - there's nobody else involved in this who I could speak to either. I kind of feel like I am being used as a kind of last hope to salvage something from this data, as he hasn't been able to publish from it yet, despite having gathered it for years (in fact he is still conducting the interviews). My suggestions for analytic approaches so far haven't been received well, although it feels like a double bind not having received any clarity on the issue from him.

Maybe I'm getting worked up for nothing and this is common?

Anyway, any feedback welcome. Thanks...