So, for the block validity question: that's done programmatically. Yes, PoS votes get the final say if a block is valid or not. This isn't something that someone running the node has to actually make a decision on for every single block. There is logic which can be defined such that if certain preconditions for a block are met, you as the PoS miner will "choose" not to include it. Also, I'm pretty sure you still get a vote reward even if the block doesn't become part of the main chain (someone correct me if I'm wrong).
OK. But if it's done programmatically and the rules are the same for all nodes, shouldn't they all always vote the same? I mean all 5 (I think it's 5 per block) voters would be expected to have yes or no on the block. Is it possible to have a split decision, like 3 to 2 votes? If yes, how is that possible unless the voters follow different rules?
If your ticket is called on a block and that block gets orphaned, you lose the reward (as the block is simply not in the chain). The ticket gets refunded of course. I recently noticed it happen on my local staking wallet, unless I misinterpreted what I saw.
I assume that blocks rejected due to PoS voting become orphan.