Master Planning should be run without filters. There is no standard buyer group filter so you have added it in the select query, which one have you added? Then does the demand have this? Ultimately it is not designed to run this way. The principle is you run for all and then filter, if you filter first you are likely to get incomplete demand based upon where the filter is applied in the demand-supply chain.
I dont understand what you are saying for point 2. Why are you deleting a plan that is creating nothing, regenerative will delete the last created plan anyway so not a necessary step.