Diamalt is apparently a brand name for a particular diastatic barley malt. Diastatic malt works to attack the damaged starch in flour to release additional sugar (natural sugars) for feeding the yeast and to create more residual sugar in the dough at the time of baking to contribute to crust color development. Professor Raymond Calvel was very fond of using diastatic barley malt for his many French dough formulations. He used it in straight doughs and in preferments applications based on commercial yeast. For straight doughs, the diastatic malt went into the mixer bowl with the rest of the ingredients. If an autolyse was used, the diastatic malt went into the mixer bowl after the autolyse rest period. When used with a preferment, it went into the dough as part of the final mix. In Professor Calvel's case, he used the diastatic malt at a rate of about 0.2-0.3% of the weight of formula flour. When I originally worked on the expanded dough calculating tool, after some research, including discussions with a representative of the largest malt supplier in the U.S., I recommended that diastatic malt be used at the rate of 0.33-0.66% of the weight of formula flour. If too much diastatic malt is added, the result can be a slack dough with poor performance.
I found your response to item 7 to be very interesting. Normally, you don't want to fully develop the dough during the mix stage because it oxidizes the carotenoids and will penalize final crust flavor and aroma. Salt is an antioxidant and, if added early in the mix stage, will help reduce the oxidation but maybe not completely if the mix is too aggressive. One of the reasons why Professor Calvel devised the autolyse method was to shorten the mix time and thereby ameliorate the oxidation of the carotenoids. It's possible that in your case, with a hydration of only 45%, the dough doesn't get the same degree of development as a bread dough would at around 68%. This is a subject that I will have to pay closer attention to when I get back to making cracker-style doughs, especially the color of the crumb. An overworked dough will yield a crumb that is whitish and washed out looking, whereas a properly mixed dough will yield a crumb that is creamy white.