Eddie's Dad rapes/used to rape him. Feel free to make it past abuse or change canon and have Eddie's Dad around and the abuse happening in the present.

Steve and Eddie start hooking up/dating. Steve starts paying more attention to Eddie's behavior. Steve knows what it's like to be traumatized. He knows what a trauma response is.

With sex I'd like Eddie to both hypersexualize himself and to completely freak out, be terrified of/hate sex. Steve has experienced both sides of this.

Up to you ending wise.