I over came decades of suicidal depression (as well as schizophrenia and bipolar) with a self concocted protocol which included psychedelics and now don't take traditional meds.

I read the OPs intention as "use K to get the person back from the bottom of depression and then leverage that boost in mood to start a habit of excersize"

That seems reasonable and a good approach. You want to reinvest the motivation and better mood into relationships and behaviors that will continue to compound feeling good.

I'd also recommend Gratitude as a practice and ultimately some sort of somatic work where you are encouraged to go deeply into any uncomfortable feelings with your full body.

Expressing gratitude is one of the surest paths to a better day.

One of my all-time favorite books -- "How to Want What You Have" by Tim Miller, PhD -- has as its central thesis the idea that:

1. Most people are relatively unhappy;

2. The root cause is our tendency always to want More [money/power, love, recognition] -- which stems from evolutionarily adaptive traits;

3. The remedy is to live in the present moment -- which one can learn to do by deliberately practicing three closely-related things:

  1. Compassion  
  2. Attention  
  3. Gratitude  

The book is (sadly, inexplicably) out of print, but it's popular enough there are plenty of used copies for sale. I first encountered HTWWYH in a 5th-edition hardcover, and it was transformative. Highest posaible recommendation.

"Most things are forgotten over time. Even the war itself, the life-and-death struggle people went through, is now like something from the distant past. We're so caught up in our everyday lives that events of the past, like ancient stars that have burned out, are no longer in orbit around our minds. There are just too many things we have to think about every day, too many new things we have to learn."

- Kafka on the Shore, Murakami

Under immensely troubling times - not as bad as war or famine, but much worse than a startup or relationship failure - these books kept me going:

  - The Obstacle Is the Way by Ryan Holiday
  - Mastery by Robert Greene
  - Courage Under Fire by James B Stockdale
  - Gratitude by Oliver Sacks
  - Being Mortal by Atul Gawande