You can set the default field values for the new records via the schema.model configuration (based on this how-to article
I am not sure I fully understand issues 2) and 3). Can you please check out the example, compare it to your implementation, and apply the necessary adjustments.
The following documentation article on cascading ComboBoxes (the same principles apply for DropDownLists) in general can also prove useful:
I hope this helps, but if some of the issues remain, please send us a similar isolated runnable project where the problem can be observed, so we can inspect it further, and try to provide more to-the-point suggestions, based on the specifics of the scenario. Thank you in advance.
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