Jaffar, Raven's weapon, and Lucina

1. In my opinion Jaffar is one of the worst user of LnD among daggers, that just helps him reaching attack other dagger units naturally have. (For instantce, a Gauis with A skill- Att/Def +2 -which still doesn't exist but could- would be better in any point.)

LnD doesn't bring any BS increase, so it's just good for purely offensive units. Jaffar is a pretty good defensive unit actually, good HP good defense. Fury is a better choice indeed. I'd personnally play a boost skill as is goes extremelly well with his weapon, Jaffar will always have HP advantage

Then I think poison strike is a fun choice but not really effective. Cause it keeps 1HP to the ennemy, it means you need two turns killing him anyway, and there are rare occasion that additional 10HP will matter exept for Wary fighters or Xmas Tharja. I'd take Vantage instead. Jaffar can attack mages without reprisal, but his low att, not amazing speed, and bad resistance make it risky. Vantage allows to finish them in case (and it happens) he fail to kill mages.

As C, slot, Savage blow is indeed a good choice. More useful than Poison strike, especially if playing Boost skills.

3. Maybe Fury / Swordbreaker can be a thing. But as lond as there is no good IV for Lucina, I'd focus on masked marth who offers quite the same things and you can already merge her for +2 for free to +5 for few.

1. Typically, Jaffar would prefer fury over life and death since it helps him keep what bulk he possesses, but L&D is never a bad option. Double savage with c and seal, poison strike in b, and he’ll make the opposing team face serious HP famine.

2. Frederick was built for a Brave axe, camilla was built to be killed for her Brave axe, the two winter units could run it, especially Chrom, but it’s up to you.

3. Lucina is a great hard hitter. Patch her speed up and you can either use her with life and death or fury and desperation. She hits hard, but doesn’t do quite as well as other sword users (Ayra, Mia, Soleil, Brave sword Chrom, etc.) because she has more of a dragon slaying niche than a pure brawler, and her defenses don’t help her much in that matter.

1. Jaffar can do fine with LnD. I think it's best to keep this and give him Windsweep for B so that none can really retaliate on him. Hitting only once actually even helps him, as he usually wants to spread his AOE-damage instead of straightout killing people. He can still do that in an occasional second shot. Additionally Windsweep work great with LnD.
My Jaffar will go a similar way. I actually want to give him Windsweep and Flashing Blade paired with Phantom Speed, as I think this will be really funny.

2. I funnily got two really bad Raven as pity breakers, too. I think at least one of them from PA.
However, I gave thier axes to Cherche and Frederick. As you don't have Cherche, Frederick seems to be the obvious choice.
I'd not advise to chose Camilla as you may pull a 5* Camilla one day and if you merge this one into yours you will get Brave Axe+ anyway.
I can't tell much about Winter Lissa. If you want, you could merge your Chrom (+HP into +Atk) and give this one Brave Axe and Bold Fighter. That's just insanely strong then. I wanted to do this for myself but I did not pull him.
So: the best options are +Atk Winter Chrom and Frederick. You will have a higher effect on Frederick though. Or you just fodder both Ravens, I did that too. Santa Chrom and Fred are both better than Raven.

3. I also pulled an average Lucina once and I actually used her as Aether fodder because
well... We already have Masked Marth, do we? Much easier to build, still insane Atk, better Speed.