The Snow Flurry Assassin (3.2 theorycrafting)

Just theorycrafting a build, won't be my league starter (at least three mandatory uniques - Cospri's, the other Cospri's, and Volkuur's), but one I'd like to try. It attempts to make use of the detonate-on-frostbolt mechanic in Vortex.

Also works with Cyclone, which would make it Snowclone.

Assassin base. Tree still in progress but will focus on life, crit, and attack speed, going up to witch area for power charges, pastebin from PoB here:

https://pastebin.com/7UaepHAE

Doesn't have new ascendancy, but critical ones are:
Noxious Strike - increases crit chance based on poison stacks.
Unstable infusion - generates power charges.
Deadly infusion - power charges give crit chance.
The fourth one, I'm not sure what I want. Ambush and Assassinate for the culling and crit chance, maybe.

The principle of the build is to flurry or cyclone with Cospri's Malice and Volkuur's Guidance (cold version). Chest will have cast on crit frostbolt (largely unsupported), Malice will have Vortex that will cast on the frostbolts for the 40% more on the gem. Cospri's armor will give the build 100% poison on hit with ascendancy's 40% (I tested in standard with legacy Cospri's). Curses will probably be Warlord's for leech and Temporal Chains to help with the crappy duration of poison due to Volkuur's as well as defense, likely both applied with Blasphemy, though Haste would be nice to have so moving one to a CwDT setup is possibly.

Depending on how Cospri's works, I may dual wield them and have one with Vortex and one with Ice Nova (same frostbolt detonate mechanic). Between the fast attacks and the multiple spells cast getting to enough poison stacks for max crit should be easy. The poison damage as currently envisioned isn't the point of the build, it's just a bonus on the side that helps with crit chance.

I've tried this in Standard and it works in principle without the poison part (requires new Assassin ascendancy). Specifically, I've confirmed I can detonate the crit-cast frostbolts.

So... questions:

1. Does it make sense to get the extra poison damage and the crits-deal-more-poison node, and actually make the build do more poison damage? I'm new to PoB and not sure how to set this up - the number crunching is a mess here because there are at least three skills dealing damage (though the flurry/cyclone damage is minimal).

2. Is it worth it to get the 2nd Cospri's Malice? Hard to tell in testing, but it seems like the Vortex *AND* Nova is redundant, though I do get three frostbolts per cast, so on single target if it alternates vortex/nova/bolt/repeat instead of vortex/bolt/repeat I'll get more damage since I get three bolts per cast.

3. What curses should I be using? I'd love to work frostbite in there for more damage, but Temp Chains adds defensive capability to a squishy build and the short duration of the poison is kind of a problem when trying to maintain 20 stacks on a boss.

4. Is there a better way to keep my health up than Warlord's? I know there are leech cold damage as health items, but they all have really low numbers.