Hey and welcome to the forum!
I’m a little bit confused here…so maybe you can help me understand - but why not go for the harra set instead of the demonslayer?
You seem to want to focus on cold damage, demonslayer only provides bonuses to vit damage, and in fact detracts from cold damage as can be seen by the conversion on the head piece.
Last but not least, you’d almost always want an offhand for PB because it’ll give you much needed energy sustain to keep spamming it.
Here’s a great example from which you can get some ideas 