i would not worry about the salt on the glas.. its perfectly normal... to tame it you can handle it as much as possible AS LONG AS ITS EATING ALL ITS FOOD!... if you see food left you should leave it alone.. and dont stress it out... a iguana that size can eat AT LEAST a fist full of greens or 1/3 of an banana every day (just as an reference) but dont freak it out.. handle it calm and slow.. dont make fast moves or to much sounds...
Good luck..