if this story continues, it will be a prime example of stockholm syndrome victim.

Actually, it's Trauma Bonding. Not Stockholm Syndrome.

The MC is unaware of how he was treated is considered abuse, he as conditioned and groomed to depend on the ML's dad. So, when the ML comes along, he realizes the ML is his only hope of not being abandoned. More of a "pseudo" choice subconsciously made.

Stockholm syndrome: More aware of the abuse. Often short-term and used for cases of hostages or kidnapping. Unaware of the "switch"