In order to get the guy with the boat to appear again, you have to either leave immediately without going and doing that stuff in the region, or complete all the quests in that region and then go back to the docking town. The reason why is the slight changes to the storyline don’t make any sense if they let you do both.
You already know Kratos can get Tetra Slash, again, if you’re having trouble, he can’t team up with anyone else to defeat the enemy. This is the ONLY in-battle nickname you can get.
Most of them will appear after events. One will appear after a certain story event, two others will appear after an optional story event. In order not to spoil, I didn’t think you’d want the details on these. ;) Just that they happen and the optional event is kind of obvious.
Three will appear once you reach a certain level with Kratos.
One you will get from the coliseum (come now, this shouldn’t be a surprise, every cliched RPG has a coliseum! ;))
The last one you will get from a certain meeting with the Wonder Chef.
I could get more detailed, but you’re not at any part to get more except maybe his first “level” title.
Two last things to remember in battle concerning long-range attacks with mages is that enemies will often try to get to your mages and since they can’t move while charging a spell, in the heat of battle, it can look like they aren’t avoiding enemies at all. Depending on the enemy, you can either lure them away, or intercept, but when it comes to super-strong enemies like the ones you are facing, sometimes your mages will get stuck between other characters or enemies, or get hit by a long-range attack and not actually be able to get away. You’ll have to watch pretty diligently for this.
The other thing is, when this happens, its often helpful to reverse formations (you know where their heads are listed on a graph where each of the strategies are).
In older Tales games, mages used to stay off-screen and pelt the enemy with magic in most cases, unmolested. In order to advance battle strategy, latter games starting making the enemy AI a little tougher in selecting out mages, so the the battle strategy shifted more to stunning and incapicitating enemies by watching their battle patterns. (I’m not sure if you’ve noticed this yet but every single Tales boss has a predictable battle pattern and that goes for Symphonia as well. Symphonia’s bosses are actually less varied than Eternia’s and Destiny 2’s.)
So if you haven’t been using these things yet, those are some other things you might try. :)
In any case, I’m going to sleep now, so hopefully things work out for you from now on.
-Kitsune