Year old orders not fulfilled - not sure how to clean it up

Hi Everyone, I've got a fun little problem that I could use some advice on. When we implemented netsuite we used netsuite PS. Expectations didn't match up with what was delivered and we ended up with a lack of training and a premature launch. In the early months almost no orders were fulfilled. Then lots of products went into negative inventory that prevented orders from being fulfilled. We noticed inventory numbers were off but didn't investigate. That resulted in a series of inventory adjustments to correct for the lack of fulfillment.

So now I need to untangle this thing and I've got about 400 unfilfilled orders. I can bulk fulfill some of them but a good chunk of them are in negative inventory. Those we can manually fulfill driving the inventory further negative.