Bread question regarding malt
Two different substances here. 
Non-diastatic malt powder is mostly used for flavor.
Diastatic malt contains the diastase enzyme used to promote more of the starches to be broken down into sugars that yeasts can use as food. Too much Diastatic malt will make your bread come out gummy inside. For flours that do not have barley malt already incorporated in them (i.e rye flours) a recommended amounts of diastatic malt powder is less than 2.0% of the total flour weight.