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For the steps/mm on extrusion, probably the best thing to do is just measure it. Disconnect the nimble (bolt one size together so it doesn't fall apart), feed some filament in so the end is level with the housing, and then extrude 100mm (need to enable cold extrusion). Measure the exact amount extruded and use the formula:
(amount requested / actual amount fed) * current steps/mm = new steps/mm.
Do this a few times and you will get it.
(If you were already aware of this procedure, just ignore the post)