IVs for Alm

-HP +SPD is definitely better for Alm, as it makes him better at avoiding doubles. Also, I'd recommend merging Alm unless you really need windsweep, but keep in mind that you can get that skill from a 4 star Joshua too.

Tough choice, as his defense isn't incredible and he would certainly welcome the bulk. Spd would help him to proc Windsweep more reliably, though. I think it really depends on how you want to build him, and whether you intend to use Windsweep or replace it.

As for what to do with the spare, I had a second Alm several months ago and foddered him into Jaffar for Windsweep. I've never used Jaffar, don't see myself every using him, and really regret the whole thing. I wish I'd merged the Alms. That's just me, though.

I would personally go Def boon and replace Windsweep with Renewal. The extra defense will help him take less damage, and he’d be recovering 20 hp every other turn rather than just 10. I tried Alm with Windsweep and I don’t like it. I’d much rather have the extra healing than Windsweep.

As for the other question, there aren’t too many units that use Windsweep well, other than Sothe or Felicia, or some other super speedy damage-chipper. So it’s up to you if you want to build up a damage chipper or have a stronger Alm. I personally would keep him in case you get a good Felicia. I never used her that much until she got a refinery update. Now I use her a lot more, and I gave mine Windsweep. :)