The photo of Peter didn't disturb Tony's heart, it gave him the answer to the puzzle
This theory actually does make sense. Tony looks at the photo and sees their fingers - one V pointing up and one V pointing down. Tony immediately goes to his worktable and comes up with the time GPS as a Mobius strip. He tells Pepper he figured things out, but it’s Pepper who has to point out that the two of them are part of the very fortunate few who have benefited from the Snap.
***
As Pepper washed her hands in the kitchen sink, she sighed as she glanced at the picture of the young man--or as she now knew, the underage teenager that Tony tried to persuade join the Avengers.
She didn't really know much more about the boy and his aunt other than their names. It's not like Tony spoke about them or anyone else in the years between the Snap and the return. No wonder. Peter Parker was Tony’s dirty little secret. Pepper doubted Peter’s aunt--or anyone else who knew “Spider-Man” was actually a child--would have let Tony anywhere near him. Part of her wanted to tell Peter not to take it so hard, because Tony definitely didn’t feel the same.
Pepper glanced at the photo again. She remembered that day, when Tony rushed from washing the dishes to his workshop. It was the same evening he offered to destroy his research that might have fixed things.
Pepper like to think that it was seeing Peter's face that spurred Tony to do more research. She knew that it wasn’t, because Tony was fine with letting Peter--and everyone else--stay Snapped. She’d had to play on the idea of Tony not resting to get him to agree to share his invention with the others.
She picked up the photo as she turned and made her way back outside. Pepper would give Peter the photo. Tony didn't do well by the young man in life, but at least she could preserve the illusion that Tony cared.