Gonzalo, to answer your first question, the tool calls out(4) 402 ohm resistors in parallel. Please see the diagram for the placement in the circuit. Rin is the one we are talking about
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The web tool calls out (burn off) resisters to keep the IC die temp below 125C. You will be dropping about 6v across Rin, and the IC will only see 18V. There will be less power burned off in the IC, keeping its temperature down.
Depending on your layout and effective TJA you may need to adjust the value of that resistor, The tool suggests 4 resistors in parallel as it is typically cheaper than using a single higher power capable resistor.
