TigerJim: If what Raze said is true about the shield doing fire damage to you until you turn it off, you probably have to turn off the shield if you want to kill Barnabus. I don't think killing him is really required to complete the game, except to the extent that it's needed to complete other quests which might give you useful rewards.
What part, exactly, about the jumping puzzle are you having a hard time with? Is it the part where you have to jump on the platforms which start to sink when you jump on them, and you aren't able to get the timing right?
As for the dragon sheilds at the Zeppelin Hanger or High Hall, I don't think you can turn those off, but you really don't need to become a dragon in those areas anyhow.
I'm not sure, but I *think* the reason those areas have the shields is that, at least notionally, although a lot of people seem to know you are the Dragon Knight in this game, not EVERYONE does. You are trying to stay 'incongito' when you are at the Harbor and High Hall, because if you didn't, they'd probably sic the Slayers on you (there's a Slayer training camp right next to the harbor, and they aren't supposed to know you are a Dragon).
So, from a roleplay perspective, it doesn't make sense for you to take Dragon Form right in the middle of populated areas where everyone can see you.
The Aleroth ministry can be challenging. Perhaps you need to adjust your character build/retrain? Maybe you just need to level up and come back later to try it again (I'm not sure what level you are)? Perhaps a few potions can help?
I don't believe you actually can enter Rivertown.
