Fanfiction.net is also a good place. Although the interface might not be as modern as AO3, it still has a lot of fanfictions. Just be sure to use the search function properly to find the ones related to Thor and Tony's relationship.
You can start by looking on Archive of Our Own (AO3). It has a large collection of fanfictions, and you can easily search for 'Thor loves Tony Stark' in the search bar. There are likely to be many different takes on this pairing there.
Chapter 453, "Secretly in Love with Jiang Yan", is the clearest early answer because the hidden truth stops feeling like mere subtext. The chapter gives readers a real answer by opening on On the cruise ship, Zheng Xun walked over with a mournful expression...
Chapter 316, "Zhao Lang Gets Jealous", is the clearest early answer because it turns Jiang Li's situation into a concrete plot event. A useful checkpoint is the way the scene starts with Zhou Xu leaned against the cabin wall, exhausted, and it took him a...
Chapter 656, "If he's the grandson of the richest man, then I am the richest man!", is the clearest early answer because it turns Mr's situation into a concrete plot event. Early on, But if she knew he was still unchanged, or even worse than before,....
Chapter 592, "The Secret of Dragon Ridge Lake", is the clearest early answer because the hidden truth stops feeling like mere subtext. Early on, Hmm?" Jiang Li's unexpected question left Zhao Lang somewhat.... By the end, It was fortunate they hadn't risked coming down earlier, otherwise....
Chapter 426, "How Did Someone Fall Down?!", is the clearest early answer because it turns Tai Fan's situation into a concrete plot event. It opens with Isn't this a bit too risky..." Liu Qian, standing out of the camera's...
Chapter 701, "Let Bai Lu and Chen'an Terminate the Contract", is the clearest early answer because it turns Let Bai Lu's situation into a concrete plot event. Early on, Miss Jiang, that move of yours was totally awesome!" Shao Changqing....
Chapter 340, "Holy Heart Hospital", is the clearest early answer because it turns Li's situation into a concrete plot event.
Chapter 442, "Let's Form an Alliance", is the clearest early answer because a shaky connection becomes usable in the plot. The chapter turns that into something concrete by moving from Chang Rong was bewildered, "So, she seems pretty impressive." More...
Chapter 483, "Why Does a Pig Eat M9?!", is the clearest early answer because it turns Bai Lu's situation into a concrete plot event. It opens with Wilderness Survival Day 11, temperature 31 degrees, wind speed... and closes on Jiang Yan had apparently gotten used to it too..
Chapter 651, "Is This... A Military Fighter Jet?!", is the clearest early answer because the buildup finally cashes out in a real clash. Early on, He Pingzhang's first action upon being summoned was to rush to the....