When that limitation gets too troublesome, you can post the first part of your message, then click "Edit Post" at the bottom of your post and add the rest. When editing an existing post, it doesn't check for that length restriction. (I do recommend having your entire post written ahead of time though, so you can just cut the excess and paste it back in when in Edit mode. You don't want to leave just the first bit there the whole time you're writing the remainder.)
I'd like to find a good listing for that, too. I've learned to recognize several of those symbols, but have yet to find a good resource that shows and explains them all. It seems really strange for this sort of thing not to be part of the game's main documentation, but I've never found it anywhere.
Well, at least two of the symbols by mob names indicate this. There's a blue double blob symbol (if it's supposed to picture anything, I've never figured out what) that indicates a mob will not attack unless you attack it first, and there's a mostly red triangular symbol that indicates the mob will aggro when you get too close. Those are the two most common indicators, but some mobs have other symbols besides those two, and I don't know what all the others mean.
The "Others" or "All" doesn't actually relate to the HP/MP/TP bars, although by default it shows up near them. It's refering to how you're set to target mobs. Under Character Customization and Targeting, you can either set your targeting to be based on whether you have your weapon drawn or not, or set several ways of manually changing it.
For instance, as a PS3 player, I have mine set so that L1+[square] changes my targeting to "Enemies", meaning as I cycle through different targets it will only select mobs. Then if I use L1+[circle] it changes to a "Custom" setting where it only targets player characters (which is useful on healing classes). Or if I press L1+[triangle], it changes to "All" and target cycling will be able to target anyone and anything. These are all configurable to whatever you want. (The L1+[square], etc. is obviously PS3 based, but I'm pretty sure there's an equivalent for PC players who want to change how Tab target cycling works to fit their current objectives.)