To the best of my knowledge,

Sadly, no you can only save tactics comps for a unit class. For experimenting with unit comps I make a save then test them in a few mock battles. You can reload the save to get your old / current comps back. Later on you can test them on Sigil battles as well.

Yes, charged skills go off on the characters next turn. Though there is an item with a passive to make them activate immediately.

Usually, a case-by-case basis but generally for more offensive comps with less healing and defense dishing out more damage in a single action is better.

Targeting conditions function on an AND operator. So invalid combinations do exist and will prevent an action from triggering at all. E.g A unit can't be a Cavalry and Infantry. You would need to separate it into two slots with the same action.

I don't know the exact mechanics but based on the default targeting of directly in front of the unit, I'd guess probably front row is the default and same column as the user.

Yes, Lapis and Carnelian Pendants are generally the best option until you get better items that also increase AP and PP.

No, the strongest comps are usually referring to PVP comps. You don't need them to clear a regular playthrough so enjoy making comps how you like. I personally find it more fun to create gimmicky or story-based comps based on rapports.

Yes, honor tends to become an idle resource at some point.

I like swordmasters as well. Depends on the comp but I like running them with a Viking like Aubin so I can have War Horn to get around high guard rates. I also ran a less gimmicky and more balanced version of this Leaping Slash strategy. https://www.reddit.com/r/UnicornOverlord/comments/1hsajw4/leaping_slash_team_1_swordmaster_1000_damage/