help with my poet's pen poison bladefall agony/purity pathfinder

This is my first character in a while and I'm very rusty. He's going strong at 81 and is fun to play, but I'm not sure how to finish off his gear. The coming calamity lets me run 3 or 4 supports + agony + purity. Agony does a lot of damage against trash and bosses, purity lets me play agressively without needing to reposition often (important since I don't have a movement skill) and does pretty good dps on bosses, and the armor gives me 70 of my 98% stun immunity.

2nd poet's pen vs spell dmg/crit shield: I'm not sure what spells I'd put in a second poet's pen. I could do an elemental spell and use volkuur's, but I'm not scaling elemental damage. I could do something that hits frequently like ball lightning, for heals. Maybe with despair?

If I don't use volkuur's, what gloves should I consider. I'm running the embalmer atm, which I haven't been able to recolor for my frenzy link just yet.

Ideally I'll use impresence so that I can run a despair aura. That'll be a while, though. Despair in second poet's pen would alleviate this expense. Not sure what I'd run on neck in that case. Just a rare with crit stats, life, resist?

The final tree will be something like this:

I should have gone assassin for the extra poison chance. That'd have let me do something like this: