Sweet Squeeks! What a beautiful story about him and his wonderful life with your dad (and mom). It sounds like it was a life full of play and shelter and love, not only with his humans but with his tortie, Isabelle. The description of their hugging melted my heart. I'm sure they will meet again when she crosses the bridge. For now, he will make friends with all the others up there until it's her time.
Prayers that your dad's heart will heal as well as your own.