Who to five star round 2

Xander or Lloyd.

Xander is good because he is good for Horse Emblem and has a DC sword.

Lloyd is a really good mage-tank and with DC can counter mage units with the right investment and set.

Edit: By the way, why would you put Xander on the list of possible units to 5* if, judging by the tone in your post, you don't want to 5* him? So confused, lol.

Honestly, it looks like you have more than enough heroes. Unless you're itching to complete a pony/peggy/armor team, just save the feathers for the future or spend them to merge into a unit you use in the arena.

Xander has quite lost his place in the meta and his most common build has been triangle adept+sword breaker which is kinda sad but he is still a pretty top tier unit.

Otherwise, Catria +Spd/-Res is acually her optimal IVs

I'd personally say either Xander or Catria for the following reasons.
-Xander is probably the best overall option considering he has DC in his weapon and is still a solid tank. I understand if you think Sigurd and Siegbert are fine for sword cavaliers.
-Lloyd is alright, but I personally believe Joshua is better.
-I would wait until you get a better Kagero, especially if you plan on keeping her Poison Dagger.
-Barst does have solid IVs, but I think there are better options at axe (unless you love Barst).
-Catria's IV's are great and is a solid unit. I would promote her if you do not have Tana, Cordelia, or Hinoka.

These are just my opinions on the subject.

Definitely save your feathers for the upcoming ??? GHB.

If you don’t want to do Xander, hold your feathers. Compared to other units you have, your other options for dropping feathers are lackluster.