Spitelout is definitely Snotlout's father. Tell me that you can't imagine Snotlout giving his hypothetical future child the same advice his father gave him in this episode?
If the show was prone to doing deep, emotional episodes, I bet we'd have something that really delved into the inner workings of Snotlout's brain. As it is, this episode did a really good job of showing us how Snotlout has these deep-seated insecurities without losing its humor.
It was nice not only seeing Snotlout's insecurities acknowledged but seeing him overcome them and realize that he should do what he, not his father, wants.
This season has done a good job showcasing the relationships between the characters as well. How the rest of the group dealt with Snotlout in this episode was nice to see, including Hiccup letting him act as the leader because he could see that Snotlout needed that confidence.
It's not that I don't think their friendships was shown well in the other seasons. Season four just really seems to have showcased them, and as someone who has such a deep appreciation for fictional friendships, I've enjoyed that.