Sorry if you think I'm hounding you with a third post but I would really you love to see you start to think differently.
Big vocabulary - you don't need it. Your job doesn't require you to swallow a dictionary. Effective communication isn't about big or fancy words, it's about explaing things clearly so they can be easily understand.
Knowledge isn't where you want it to be - do you think there's a possibility that you want to know everything now? Are you being fair to yourself? Learning a role is frustrating because you can't do it all immediately. You have to build it up over time. All you have to focus on is do you know more this week than last week? Just keep building on progress.
Hate seeking advice - how else will you learn? I often take on new staff. The ones that don't contact me often or rarely ask me for advice are the ones I worry about most. I know there's a lot they don't know so I expect questions. If they aren't checking things, what are they doing. Winging it isn't a good idea and it goes wrong.
Manager gives better advice - yes and she should. She had before experience and is paid more. You will built upyour knowledge over time.
Council estate - what difference does this make to your job? If assholes judge you, it's cause they are assholes not because of your ability to do your job.
Siblings as criminals - I don't mean to be dismissive but again what difference does your job? It may impact your life in other ways outside the workforce but not in it. (I also work with people in the same position, some keep it quiet, others openly mention it. If anything, I admire them more for taking a different route as not always easy not to be influenced by siblings).
Work is about output and results. Honestly that's what really matters. Your attitude, how you get on with people, your work ethic, your willingness to learn etc.
The fact that you care so much tells me you're good. People who are terrible at their job, never feel like you.