Bio weapons, not so much. They are capable of weaponizing biological warfare agents, but do not emphasize those pursuits like they do with nuclear or chemical weapons. Bio is too hard to control, and there is too much potential for it to backfire. In close quarters and with virtually no medical infrastructure if the disease finds its way home, going bio is not an attractive option for the DPRK.
Chemical weapons, well, you name it. They've pumped out a huge stock of nerve, blister, choking and blood agents and can fire them from just about any indirect fire platform they have, from SCUDs to mortars. They have a serious investment in chemical training and equipment for their troops (and civilians) at all levels, so they can operate offensively and defensively in a chemical environment.
Their concept of use is to hit the front line areas with non persistent agents that will clear a path for their advancing units. They will use persistent agents deeper south, on cities, logistical nodes, etc, in order to cause delay, panic and confusion.
Their chemical arsenal is vast and horrific. Chemicals are 'poor man's WMD', and not nearly as effective as nuclear weapons. Still, in such large quantities and down so narrow a peninsula, they could cause staggering casualties.
schedule for moving our troops to a safer area?
The details are still being ironed out, lots of moving parts to fiddle with. It will probably be incremental, and partial, but we'll have the bulk of our guys at a safer distance within a couple of years.