I wish I had more time to answer this better and do a bit more research, but I regret this is the best I can do right now:
- The Twitter API (and the format of tweets) has almost certainly changed since 2018. It seems to change often.
- A change announced last year may or may not be relevant to you.
- Archive Team has a page about archiving twitter in which they list some tools that may be helpful in this context, as well as mentioning some notes, such as how to get the full-sized version of images embedded in a tweet.
- There are other tools not mentioned on the Archive Team page, such as SFM and Thread Reader.
- I’ve personally given up on saving tweets in HTML format. Yes, proper archiving best practices would probably say web archives should be stored in WARC format, but in my experience, the saved content is invariably broken when I view it (e.g.) a year later. Plus, if the author deletes the original tweet, then things are even worse.
- In another forum posting, I described some things I do. Basically, I resort to saving a PDF rendering of the tweet.