How should one address negative circumstances with past advisor in a Statement of Purpose?
Congratulations on the switch, I'm so glad to hear your update.

There will be an ongoing need to heal from the trauma you underwent.  The SOP will be separate from that.

If you are concerned that an admissions committee might raise a red flag for the extra time you spent in your program, you may address that briefly in a cover letter.  For example, "You might notice that I spent longer than customary on my degree.  That was due to some health issues exacerbated by an uncomfortable advisor fit."  That's enough.

You might also alert your new advisor to your concern, so that s/he may choose to consider this when writing letter of recommendation.