Pts league. 2nd place in a 14 team league. 50 pts behind 1st place. I would be the one moving Past and Gibson. It's a cap keeper league but I am more concerned for this year. ($80 mil cap. Past $4.4 x 2 more years after this. Gibson back in draft pool. Skinner $4 x 3 more years after this. Dub $8.1 1 more year after this season.)
Hard to pull the trigger on moving a 90-95 pt F who is dirt cheap. Is Skinner now a legit 70-75 pt F though playing with Jack? If so I'm thinking the upside of Dub over Gibson is enough to pull trigger for a push.
The goalie exchange seems like a minor win because of the extra year you're picking up, although $8.1 for Dubnyk seems a little pricey.
Remember that Skinner is a UFA after this season, so he's no guarantee to be returning to Buffalo. Worst case scenario is that he signs with a team that ends up using him like Carolina did, which means that 70 points will be a pipe dream. Either way, Pastrnak is a great scorer with a great contract, and you'd have to knock my socks off with an impressive offer if I were you.
I'd keep what you have. If you're looking to improve your goaltending, I'd look at other possible deals or the waiver wire.