[2.2] Bladefall Trap build questions

Skill tree: http://poe.rivsoft.net/517173651

Main Gems (5L): Bladefall, Trap, Poison, Multi Trap/Cluster Trap, Trap Damage
Solo mob Gems (4L): Bear Trap, Poison, Trap Damage, Cull

Questions:

Bow and quiver for this build? Dual daggers? Dagger shield? I'd rather stick with a 6S main hand because then I could reliably get 2 5L set ups for both my bladefall and my bear trap.

If I have the trap in a bow, do physical damage with bows skill nodes double dip through my trap and into my poison? Or only if I was using a bow skill?

I was thinking about running spell totem + vulnerability + wither for my curse and utility.

Definitely dagger and shield. It's the safest option. You can fit plenty of HP/res there, there's always 20%+ chance that you'll mitigate damage completely by blocking it. If you have plenty of life and res already, you can use 3L Jaws of Agony shield, which is superb for poison bladefall trapper.

This build does not benefit from dual daggers. Using bow and quiver is not an option, because you want to use a dagger and whirling blades to me very mobile.

You don't need double 5L for this build, it's redundant. There's no benefit from using 5L in a bow and 5L in a chest.

Your "main gems" combination works exceptionaly well for both single targets and mob packs (with chain reaction passive from saboteur tree bladefall volleys will always overlap thus inflicting many stacks of poison).
It does not matter if you have trap in a bow, bow passives won't apply to poison damage nor trap damage.