Filtered water should be fine to use.
Citric acid may be okay to use. Since you have been making and using MMS1 with it and have not reported any discomfort, then it is working for you. Some people have stomach problems when using citric acid.
No, CDH is not the same as MMS1. MMS1 only contains 10% of available CLO2 when made, so for use topically there is not much CLO2. There is residual MMS and citric acid, however.
CDH is 50% activated, so there is more CLO2 available for topical use. Both CDH and CDS contain 3000 ppm CLO2 when used externally. Used internally, CDS will not increase in CLO2 content, but CDH will increase its CLO2.
Regular CDH takes 8-12 hours to activate. There is a newer version that can be made in 5 minutes.