Well, I imagine that you could glean some iron by trying to eat it. But if you are really worried about your calorie intake I think you could take the anchor out and leave it home. The temptation will be gone then. Just take the empty bag and no calories are in the bag at all.
Not sure mine is stainless steel. If so, it’s painted, but either way I wouldn’t hesitate to use it in salt water. If you’re concerned you can always rinse it off with fresh watwr afterwards. It’s a pretty stout little unit.
3.5 of course. it will be hardly enough. 1.5 will be too small for sure
I have a 12 foot Jon and use a 12 pounder that seems like it's just enough. I wouldn't go less than a 15