1. Look Trudy quest up on wiki, it exists so you could do exactly that
2. Goblin option is a Kylira quest
3. Well, companions ability to get fucked depends on affection you've built with them, so if you repeat scenes that give you their affection many times, they get fucked earlier. You can only get Kylira fucked only in combat, probably.
Honestly, giving goblin birthes was already overcomplicated and even buggy, making eggs disappear at random point, but there's an Ending that relies on you doing it TEN times, and now it's further complicated by swinging other characters with her.