Bradley can survive Arihama. Didn't you made your crew level up too? The best way is by sending them in the missions, and also grinding them up with repeatable enemies (The nearest would by the Wyverns of Silent Plains).
Your crew can level up too, check their experience bar in the mission tab too.
Mine in my first mistake was not making my crew level up, and Hakkon died but I reset it up grind a little more so they'll raise their endurance, damage and accuracy (lesser miss when giving damage to enemies).
The only available RPG grind in this arc to join you is Chip (The Ship's AI), Rylan, Bradley, Cicero, Phoenix, and Feraldo. (Those are the crew that can level up with grindable enemies as well as GA and GU missions.
Meanwhile, Hakkon, Skru'Vaks, are the only people that can level up with using GA and GU missions, they can't participate in the repeatable grind but they will join you in battling Arihama.
Riordan can join in the battling Arihama but this is the only unit trooper that is unable to level up through both GU's/GA's mission as well as normal RPG grinding.
But going back to the first question, if you want your mc to be damage dealer. Ranged weapon is suitable, rather than the sword which will come later whereas all your points are spent in the stats unless there is a weapon for melee, but I think you can have the sword when you gotten it after you save Alastor the Gunsmith in the prior arc. But the full sword talents also comes when you hire Feraldo after the hiring sidequest.
Plus the sword talents are grueling to keep up since your mc's experience bar is higher in this part and all your stat points and talent points are spent in earlier available stat and/or talent which are the ranged skills and the initiative boost if I am not mistaken.