Has anyone determined the best times to add these items to cures to assist in color maintenance and assistance in lowering nitrite/nitrates in the curing process?
First say to yourself what you would be; and then do what you have to do. - Epictetus
This is a pretty thorny issue as nitrite in conjunction with sodium ascorbate - erythorbate will reduce nitrite to nitric oxide and other products within 20 days.
This leads me to believe that nitrite with ascorbate/erythorbate alone would not be ideal to dry cure bacon alone. therefore a combination cure with nitrite and about 700 ppm potassium nitrate would be better. if the cure was applied in several applications then applying ascorbate in the last application would make sense to me.
The application of ascorbate / erythorbate is really only applicable where the bacon is going to be Fred to avoid the formation of Nitrosamines. The following link might be of help.