As for pruning, we can definitely do it structurally, but the store is append only, so this implies a local rewrite of the store to reduce it's size (i.e. compression). I documented the queries to make sure it was possible. Inclusive of purging unconfirmed. But it's probably faster to just resync for that, and not worth it because it's so small. But really I don't see pruning as important. It's bad for the network, the storage cost for the full chain is currently like $5 and dropping (even with growth considered), it adds complexity and limits functionality, it will eventually be totally inconsequential.
Yes, no pruned node can reorg past its pruning point.