The fee problem came up over and over again during the Chaincode Labs Lightning seminar. Predicting fees reliably is just impossible they say - lots of potential for feedback which breaks attempts at making reliable public fee estimation algorithms - so you need a way to respond in real time.

PTLCs are a fun privacy math hack. This jamming attack is new to me. It seems like it isn't possible for a node to prevent a cycle when it doesn't know anything about the route which is the whole goal of PTLCs. I suspect the solution will involve another cryptography math hack that somehow busts cycles.