Let me say this if I may

You are/were a teacher, and you know there is no magic bullet.  Accent reduction is about effort and practice.  There is no wiz website.  You already have an established lifestyle.  Given another 20 years, do you think you can do better than the past 20 years?  On the other hand, it's already been 20 years, does it really matter to live with a Chinese accent for another 20 years?
No offense, just my 2 cents.