What should I do about my previous self-plagiarism?
This following response is highly personal and does not claim universality: it is my personal 2 cents, and my opinion is that your approach sounds perfectly fine. You do not claim other people's results as your own and you do not claim previous results of yours as novel. 

I do not know where this fashion that one has to rewrite everything from scratch comes from, even unchanged aspects in a new paper. Perhaps it comes from humanities where language and formulation is central. But in technical topics it does - in my personal opinion - not really make sense to reformulate obvious intro sections; as little as it makes sense to rewrite code for which there is a library. 

Personally, I like to rewrite even intro material sections because I do not like to bore my readers that have read other papers of mine, and also I sometimes discover novel aspects just by writing. However, as long as above conditions of 1. attribution and 2. clearly delineated novelty are fulfilled, I would not join in a negative judgement about repeated sections.