Bonzo Banana

I don't know about this specific part but know DNP do naff 10 speed freewheels which when used with a freewheel hub with slightly non-perfect threading (common) you get problems because of the tight spacing of gears with freewheel wobble. You see many cheap bikes with 8,9 or 10 gears and you assume at first it has a freehub and cassette and instead has a DNP freewheel and so you effectively have gearing less accurate and more problematic than even entry level Shimano freewheels. For this reason I suspect DNP are not a company that has much concern for product quality or reliability and it is best replaced with a Shimano freewheel or if you can stomach the extra money assuming 7 speed replace the rear wheel with a 20" freehub wheel, 7 speed cassette and spacer. Over here in the UK that would probably cost either £10 or £40 minimum but don't know the prices elsewhere. I'd assume your chain would be ok to re-use. I'd hope so after only 300 miles unless damaged.