I'm just going to touch on a couple of your questions due to time, but others will chime in I'm sure and, hopefully, get to all your questions.
You shouldn't need the calcium and vitamin powder. Your ig should get all it needs from it's foods.
Does your Walmart carry collard greens? Of all the greens, they seem to last longest and may in fact be the best choice for your iguana.
Mustard greens and turnip greens are also good options. Problem is they just don't store well. You may get a week out of greens before they get too bad to use. Sorry, but that's just part of the cost of owning an iguana.
"Large femoral pores" usually indicate a male.
Iguanas "snalt" (sneeze) to remove excess salt from their system. Quite normal.
Gotta run, hope I can get back for more.