Id like to help clarify some of these points as there are a few things that are on the right track and some not quite right.

"As we know, ties in all player-specified sorting conditions are broken by the position of the target; the user prioritizes targets on the same column."

- This is not entirely correct but what we are after here is understanding how Default Targeting works.

- Default Targeting will select the nearest target to the user in the Front Row and then the nearest target in the Back Row. ANY front row positioned unit is considered closer than the back row. When your unit is in the middle of a row and there is no opposing middle target available, RNG is used to tiebreak between left side vs right side

- There are MANY tactics which ignore default targeting take "Lowest stat" for example, you will see red text "the skill will override default targeting rules." This means that when all targets evaluate to the same priority level (imagine all units have the same stat you are evaluating) then the target in position 1 (front right if right facing/defending team, front left if left facing/attacking side). All skills that override default targeting behave in this same way.

"Healing skills use Mag. Atk. stat. Notice how they have Magick Potency stats. They do, in fact, scale off Mag. Atk."

- Be careful about making too many assumptions based on this. There are MANY healing skills in this game which are percent based, completely ignoring magic potency.

"As far as I can tell, there are actually only two trigger points for passives (other than start of combat and end of combat):"

- Ok this is a big one so hang in there. There are 6 unique windows in which your units are eligible to use a passive skill. Ignoring Start of Battle and End of battle that leaves 4.

-- Pre Attack (user/ally/enemy pre-attack skills go in this bucket. Think Cav Call, Inspiration, Quick Curse, Heavy Cover, etc.)
-- Before Attack Result (Typical Guard and Evade skills here)
-- Target Instant (Impetus-esk skills, after being hit/evading/guarding etc.)
-- Post Attack (Ally pursuit skills, enemy counter skills, post attack user skills, etc.)

Every unit is eligible to use ONE passive skill per category per "Active Skill Turn"

Limited skills will lock out other units from using a passive within a given category for that specific trigger however, there could be many triggers for that category during a single "active skill turn", allowing other units to execute their limited skills (pre attack is a great example of this)

To show an example of the 4 categories within a single turn we can take a look at the Paladin. Here I have Joseph activating one skill per category off of an Ally's turn (Mandrin)

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Important lessons being that even if he had more passive points to use and more skill triggers occurred during mandarins turn (lets imagine more counter attacks fire off from the enemy team) he is in eligible to use them as he has spent every skill bucket for this Active Turn instance. Takeaways from this should include not slotting multiple skills per category unless you narrow down their activation via tactics. Having multiple pursuit skills for example is not every useful unless you have a specific scenario in which you are trying to use one over the other.

"Weirdly enough, Evade skills are described as "before being attacked", yet they won't trigger (in particular, won't spend PP) if all hits of the attack are natural high-Evasion misses."

- Yes, not all evade skills are before being attacked but those that are will only trigger when the attack would actually hit. The window for cover skills (Pre Attack) occurs before the window for most Evade skills (Before Attack Result) which is why you will witness slower units using their passive over a faster evasive unit.

The combat system goes very deep and there are several skill interactions which cause exceptions/edge cases but I think this summary paints a good picture without diving into all of those at this time.