OK, a lot of questions about the engine of Galactic Adventures. Let's see...
You can't avoid the fireball attack that the Epic can use on you, it's always like this since the original game and you can't counter that move. The fireball is a ranged weapon, meaning it can only use it if your captain or an enemy is in a distance, it can't do it if you're close to it. To prevent the Epic from using it in any adventure, you have to set the awareness about 22, any number higher than that you cause the Epic to use the fireball attack. Sure, you can set it lower than that, but if you plan to go for close-range combat where the Epic follows you and attacks once it's up to you, I recommend you set to 8, but don't go lower than that since it'll not attack and it at least needs some to do anything.
The "Power-Up Armour" is an temporary effect your captain can get to increase its defense for a short period of time. Case and point, when you get hit, you take less damage. No offense, but I'm not sure why you asked this since it should be self explanatory if you played RPGs, other games and even Spore and GA itself with the Health Boost parts and the Zealot amour equipment you can get.
The reason why GA won't let you pick things up like eggs and creates because they aren't handheld objects. The engine GA uses when it comes to props and gameplay objects is limited, but Maxis kindly programmed a way to make those things act like the way you wanted for the most part. If you want to hold eggs, you need to load a key from the gameplay objects tabs (doesn't matter which colour, just make sure the gate with the same colour isn't into play depending on the adventure you're making), set it to "Disguised", choose "Objects" on the top left corner of the screen and select any egg. It's small by default due to the size of the disguised object but you can make it bigger by holding Shift and scrolling up on the mouse wheel.
Just to let you know, you can set goals to give the key object to someone else, but other gameplay objects may not have the same goal functions due the way they were intended to work normally, like bombs, which you can only move to, not pick up. The downside with gameplay objects is that you can't disguise any object from that category into another of it's same type, so that means you can't disguise keys with Crate Classic. If you want to do that anyway, you need to make a crate in a separate editor and disguise the key with your creation, or if you modded to create a duplicate of the item which works as a fixed object.
If you're wondering about mods for GA, yes, like Camben said, there's Adventure Props. Like all mods with illegal parts, if other people need to open the creation and your adventure, they need to get that specific mod first. However, EA and Maxis don't recommend you share modded creations on the official Sporepedia since those parts aren't legit and it could ruin other games if the mod wasn't installed. However, you can share it elsewhere, even on this site if you wish.
Ripper of Spore: Unofficial Galactic Score and... that's about it.
"Raggedy Ann scares me!"