Thanks for the in-depth review! I'm glad you enjoyed the game.
Your suggestions are great too. I had already intended to have some kind of lock-out when you fail a node, but didn't have time to implement that. I hadn't considered making lower valued nodes easier/shorter codes. That's a really good idea, but I think your idea of having to have another node next to one before you can attack is totally inspired! You'd have to consider how you could restart if a team had zero nodes remaining, but that's pretty easy to solve.