Yes, he does. I haven't figured out an exact weight for him though.

For the first question, look at this doc here.

For the second question, Tucker was pretty keen on making sure that all members of the offensive team knew each other so he made sure that they met at least once. When Kamil joined the team, Tucker introduced the offensive team to him. As for how Tucker met Kamil and why Kamil joined in the first place, those will be revealed at a later point in the story.

Each route are mostly  unique to each other. Only a few days share the same scenes across all routes (The first half of Day 2 is mostly the same across all routes aside from a few dialogue changes) and the rest of each route are different.

3 arcs/acts for each route. None of the routes necessarily tie into each other since the events of each route are so divergent from each other but love interests might play a role in other routes (like how Owen plays a role in Brendan's route for example).

And I can't do anything about the skip thing. Just don't skip during animations.

Kamil was a genuine friend to all three of them. That said, he knows that Tucker is mean and a bad influence, and he doesn't partake in the bullying that the terrible trio do.