Phosphate will help keep the sausage moist. Be careful though, to much and you will have mush.
SE will help maintain color in the meat as well as help the cure when used in a brine.
Corn syrup solids will help bind and aid in fermentation, hold moisture and are 40-50% as sweet as cane. Try not to exceed more than 2% - 3% max of the green weight of the meat.
I will have to disagree with Chef Jimmy on the cure #2. Its not always needed for dry cure, you can dry cure with cure #1 with refrigeration. Meaning the end product will not be as shelf stable and will require refrigeration or freezing if not eaten within a week.
Just have fun with making your own.