Mongrels discussion

After finishing the book, I'm left with some questions, hopefully someone has an idea!

1. What happened to Darren in the end on the cruise ship?

2. Red = Trigo? Or why does he/Grace have Red's el Camino? So Grace-Ellen has a 19 year old child with Trigo, Libby was married 8-10 years before to Red, but Trigo died 3 years ago while living with Grace? Is this what grandpa meant with 'a good man can be a bad wolf'?
He was good with humans but not with wolves?
And Libby never looked into the freezer or seemed emotional learning of Trigo's death, so maybe Trigo got the el Camino buy killing Red?

3. What's your interpretation of what's happening with Libby in the end?

Mongrels