A few questions and some upgrade advice needed KBOC

I'm playing agnostic kboc ballista totem hiero. For context, I didn't follow a guide but instead based my build on other players on poeninja. I'm playing since settlers while avoiding any crafting except for a few cluster jewels.

1. My question is if faster casting really necessary for arcanist brand tornado setup since all other players on ninja run them. From my understanding, tornado's initial duration is 1.5 seconds and tornado is cast by the brand fast enough for 100% uptime even without the support. Wouldn't more duration be better for qol? Am I misunderstanding something?

2. Does tornado really boost single target damage and by how much? I don't know how this can be seen in pob. Also, I read somewhere that increasing aoe doesn't matter for overlap since the distance of the explosions from the tornado on impact increases with aoe as well.

3. If my pob says that my dps is 500k, does it mean my real dps is 4m since I can have up to 8 totems?

4. What's the absolute best imbue for kboc? Currently using lightning penetration.

5. Any suggestions on what more to improve? I'm thinking svalinn as my next big upgrade but I don't know what's next after that.

I tried converting my build into pobb.in format but the 3rd ring slot is not showing as well as the masteries allocated and bloodline ascendancy so here's a poeninja link https://poe.ninja/poe1/profile/BrewmasterMangix-4158/mirage/character/LiverLoverBoy