Beginners FAQ on sausage making, meat curing etc may often be found at the head of each relevant section, but here is the place to ask experienced users for advice if you are still stuck or need more information...we're here to help!
No you can't. Cure#1/2 contain salt as well. As a general rule for older recipes you can substitute 5g of cure#1 or 2 (depending on what you're making) for each gram of saltpetre in the recipe. For modern recipes I'd suggest posting the recipe here and someone like oddley will recalculate it for you.