My view as well. I am now convinced LF knows about L+R=Love ( he may not know it's Jon ) so he definitely knew about Ramsay. He knew Sansa would escape and raise an army. He knew it would not be enough and he played both Sansa and Cersei.Sansa is a part of his game. It's clear that he used her to get the Vale's army in the North. Giving her to wed Ramsey was a key in his plans to get the North. It gave the Vale a reason to go there and save Sansa from the Boltons who, according to LF, kidnapped her and forced her to wed Ramsey. It even gets him the order of the Crown to march against the felon Roose Bolton, who wed his heir to a suspected accomplice to regicide. She was pawn. That doesn't mean that he has no feelings for her, though. The problem is that this pawn is beginning to turn into a player...
1. Cersei orders him to go North, the Vale taking over the North seems legit now.
2. Sansa will forgive him for giving her to Ramsay when he wins her the battle.
3. He now can manipulate the North just as he manipulated the Vale.
4. With Dorne in chaos, the Tyrells dead, the Baratheons dead, the Lannisters mostly dead, the Riverlands still standing and so on, Westeros is his for the taking.
I think it would be ironic if littlefinger dies to the White Walkers or Daenerys, 2 factors he could've never seen coming.