I made some more changes to the deck, but to answer your questions. Baby Jace VP doesn't do too much, and big Jace is on the redundant side given all of the clues. I initially started with three Aether Grids but found I want one every single game, so I increased the count to four. Drawing multiples sucks, but not having it is worse. Plus there is lots of enchantment removal running around.
I moved Roast to the sideboard and cut Sarkhan completely. I also turned one of the Lumbering Falls into a fourth Yavimaya Coast. In place of Sarkhan I put Pia and Kiran Nalaar. I consider them a six to seven drop, rather than four drop but they provide another way to end games and interact favourably with Westvale Abbey because your thopters can chump block then be sacrificed before combat damage. For the bounce spell I went with Clutch of Currents since it lets you sequence a turn three against ramp/aggro where you play a two drop and bounce on of their creatures. As for Westvale Abbey, you can often chunp it once, bounce it, and by then you have Aether Grid to control the rest of the board.