What issue do you have with design rules. Please provide some details, it will help us to verify the problem if exists.

Pads within the same pattern may be connected with internal connections. For example, pads with the same pad number become internally connected automatically.
There are options for internally connected pads. You can right click on any of internally connected pads, select "Component Internal Wire ...

Normally traces go to pad centers except the case when geometric center of the pad is no copper (as your case). In that case the trace goes to the first point of polygonal pad outline.
You can replace the pad with two overlapping rectangular pads and route the trace to either of them.

The pad and the copper pour should be connected the the same net. If the pad has already connected to GND net, please open copper pour properties and verify which net it is connected to.

If intersected traces are on the same layer they are shorted. You can run "Verification -> Check Net Connectivity" to find short circuits and broken connections.

It seems not possible. We will consider using environment variables in the datasheet path. Thank you.

No, it's not mandatory. The shapes on the assembly layers make sense if you need to prepare an assembly drawing to someone who will actually make the assembly.

Thank you for the report. We are not aware of the issue before but will investigate it after the report. How soon does the real-time DRC become enabled or in other words how frequently do you have to disable it? Do you have an observation what toggles the option?

Thank you for the report, we will investigate the file and Kicad import.
The first thing I see is the file was generated in Kicad version 9.0. It's very fresh version, Kicad import in DipTrace was created and optimized when older versions of Kicad were available.

You can try "Route -> Routing Setup -> Settings" and enable "Neck-down Traces for Small Pads" option. The software will automatically reduce width of small portion of the trace to the pad width.