Well, Sonic is a hero at heart. So when Amy gets hurt, he would first assess the situation calmly, but inside he'd be worried. He'd make sure she was stable and then look for the cause of her injury. If it was an enemy, he'd go after them. But he'd also be very gentle with Amy, talking to her softly and reassuring her that she'll be okay. He'd do whatever it takes to see her back on her feet again, like finding special herbs or items that could speed up her healing process.
For Amy, she could become more understanding of the 'evil' or opposing side. Instead of just seeing Metal Sonic as a bad guy, she might learn to look deeper into his existence as a creation. This could make her more empathetic in general.
Well, usually in these fanfictions, Tails meets Sonic during an adventure where they both end up at the same place by a series of coincidences. Their meeting leads to an exciting partnership.
In many Sonic Boom fanfictions, Tails often meets Sonic by chance during one of Sonic's adventures. Maybe Sonic is in trouble and Tails shows up to help.
Tails would probably be very helpful. He'd use his intelligence to make sure Amy has a comfortable pregnancy, like creating special devices for her. Knuckles might be a bit awkward at first but would ultimately be very protective. He'd stand guard to make sure no harm comes to Amy and the unborn baby.
Some fans might be very shocked and disappointed. Sonic and Amy have a long - established relationship in the Sonic franchise, and this would be a huge deviation from what they expect.
There are many interesting fanfictions about Sonic and Amy's love. Some focus on their adventures together where their love slowly blossoms. For example, in some stories, they might face a powerful enemy together and through that experience, their bond deepens.