Can't really help with the spider templatewise. Best I could suggest is first lightening the color of the skin, then finding a spider somewhere and slowly coloring in sections so you know which part is used where. Boxing said spider in with glass blocks would probably also be helpful.
That's not a problem.. its on purpose. When hearts empty in LttP they become white rather than black. I made the armor icons go to black to differentiate the sides, and because the shield already uses white and it didn't look good.