I've not used the powder for this, but would guess that a around 20-25g of powdered peppers would give a similar kick to 100g of the hot paste as its a fairly major ingredient. You might want to up the mirin a bit and add a similar amount of say bean flour/curd or maybe rice flour as a binder, lest everything is too runny.
One thing that works really well with this and makes it quick is to slice the belly first (quite nice thick slices) and then tie them back together again as they were (I've even used wooden skewers to rebuild the belly) once you've given them a douse in the mix.
This way it will cure and be fully ready to use in a couple of days and mean that you get the full hit on every slice !!
I've found it a great twist on the usual Jeyuk Bokkeum