The cleanest (and easiest) solution I can think of is to use my Tippy Tooltips add-on.
For now, it doesn’t support extended editing, so it’s only suitable for short tooltips. But in the future, I will extend its functionality.
Furthermore, with an extra script (included in sample note type) you can automatically convert Wikipedia links into preview-tooltips:
Take a look at the first three cards of the note “History of Medicine” in the sample deck (which I updated right now) to see how I would use it.
If something doesn’t work, please don’t hesitate to report your issue on the support thread: Tippy Tooltips [Official Support]