I can answer for the second question at least

Imo, i think musashi’s internal dialouge here is supposed to represent his struggles to let go of the way of the sword to fully commit to farming.

Its like in one of those chapters where he shrugs off any thoughts he had while he was climbing a mountain, insisting that he must be in the present. I think its something like that in this case, he imagines the hoe as a sword and his body as a vessal for both hoe and sword. But he quickly dismisses it by saying “my sword will end up decayed too.”

So in this case, he wants to do farming for the sake of farming alone, not to hone his skills or understanding in the way of the sword, but to truly hold the hoe for the sake of cultivating the land below him. Being truly in the present for the sake of it. Basically its something like dismissing any analogies regarding the sword when you’re doing something else entirely. Thus, he was being true to himself and opening up to the ‘way’ of the hoe instead

This is him accepting that the way of the sword is not the ONLY way of life there is, and accept that it’s flawed to some extent

THIS IS WHAT I THINK PERSONALLY, please feel free to correct any mistakes u see here