My best guess, would be to say that, given the context, you just allow those who are capable of breaking said fourth wall in your work to be aware of the foundation of your non-fiction universe existing around them like you said.
As in, on rare occurrences, they are aware that this is the author reflecting on his memories as though it where a fictional work. Understanding they are still elements within a book, whether the events are fictional or not is perfectly fine in my opinion, "breaking the fourth wall" is still a perfect term and practise to make such a work entertaining.
I'm sure you had ideas in mind to begin with, but simply knowing these people from your past who'll be you're characters makes gauging there reactions to spontaneous events more organic, and thus all you have to do is decide if it is just you (if you are the main character, I was just assuming, lol) or everyone (in perhaps something a context sensitive manner) that is allowed to break the fourth wall.
Having never seen much of Deadpool, and only hearing comments from others around me about it, I can only hazard guesses as to the contents within the movie that has inspired you, and what you are trying to achieve. So I think the best move would be, since it's resonating in your mind still, that you maybe look at the movies use of the technique and measure it against what you have planned out so far. Maybe even watch it a second time if you feel there is something you could learn from doing so.
Simply thinking for a moment, when using it in this manner, asking questions such as. How often did Deadpool break the fourth-wall? How often did other characters respond? Would you have done it more, less, or was the movie perfectly executed in that regard in your own opinion? Lines of fiction and non-fiction isn't the issue in my mind for this, in writing you can do as much of something as you like, fact or fiction. Not knowing you well enough to make a judgement call, the best thing I could say, is a lot of humour could be derived in fourth wall breaking in terms of things that you, the author/presumed narrator are including that focuses on regrets, dwelling, and regardless of whether you're over it or not, things that creep in from your past and cause you to think "I can't believe I said/did that"
Sorry if this seems like a long read, but in the end it's a difficult one to hammer out perfectly, since humour is very much subjective for everyone, but since your idea does sounds interesting enough in concept, I couldn't resist trying to help. I hope that in then end, your project comes together for you in way that you're satisfied with. Good luck