In certain comic arcs, Pietro's fate is that of death. However, comic universes are complex and his status can vary depending on the specific storyline and alternate realities.
Wanda and Pietro did not date in the comics. Their connection is that of brother and sister, and the storyline doesn't depict them in a romantic relationship.
In the comics, Wanda and Pietro did not sleep together. Their relationship was more focused on their superhero activities and family dynamics rather than anything of that nature.
Clint could start by providing a safe environment for them to practice. He might find an isolated place where they can freely use their powers without fear of being discovered or causing harm. He could also introduce them to some of his friends who have knowledge about powers or combat skills, like Natasha, who could offer different perspectives on how to control and enhance their abilities.