The Vampire Diaries alum, 42, shared the personal story on Instagram on Friday, May 21, while wishing her a happy belated 33rd birthday. In the post, he said he owed Nikki so much "gratitude" for saving him from the bad business deal a few years ago.
He addressed his love letter to "This mama. This human," and wrote, "I've never disclosed this publicly, but this woman worked selflessly for 2yrs to build me out of a terrible business situation I got myself into."
Before the couple got together, he apparently built an "important" company while playing Damon on The Vampire Diaries from 2009 to 2017.
"I invested heavily, I made huge personal guarantees to banks," Ian wrote, before alleging, "However due to greed and fraud within that company and fraudulent activities from our biggest customer, not to mention the temporary collapse of the oil and gas industry - I was left in an EIGHT- FIGURE hole."
While not disclosing the name of the business or its associates, he revealed, "It was awful. A true nightmare day in and day out."
Ian tried to pay off his "massive monthly six-figure bank notes" by traveling the world for work, even ending up in the hospital four times in two years, he said. (In 2019, the star revealed that his Netflix show, V-Wars, "put me in the hospital," but didn't elaborate.)
"This woman here decided that she didn't want to see her husband ruin his body/mind/spirit and pulled up her bootstraps and got down in the trenches assembling a team to get to the negotiating table to find a way out," Ian continued. "She devoted her life to getting me out of that mess and it almost killed her along the way. I am where I am BECAUSE of this woman."
After the Twilight star swooped in, Ian was able to move on and build his new company, Brother's Bond Bourbon, saying, "I was able to start my life over because of this woman."
In retrospect, the alleged fraud has been "the most eye opening and truly humbling experience" for the Lost actor, he said.
As the dad to 3-year-old Bodhi recalled, it was "painful as hell but as a family SHE got us through. It's unreal. I owe her my health, my life and my sanity."
Needless to say, he said he appreciates "Nik" more than anyone, writing, "Happy 33 you incredible angel of a person. The light you radiate into our household and this planet is beyond inspiring. You are a superwoman. You made it possible for me to live and build my dreams and to start my life over."
He adorably signed the social media note with "Love," from "Ian aka Baby Daddy."
The pair welcomed their daughter in 2017, the same year the Thirteen actress founded her own business as well. She started the lifestyle brand BaYou with Love with a mission of creating sustainable fashion.