I don't know about "metallic ionic Colloidal Silver ", never heard that term before though I would expect it is the same.
9999 silver is about the best you can get commercialy, it is 99.99% which is good enough. You can get it from jewellery supplies wholesalers, some CS sellers on the net or you could just buy silver coins/bars & use them.
It doesn't matter if you remember which electrode is positive or negative although is you aren't changing them over eventually the positive electrode will get worn down. I just disconnect the electrodes & each has a 50/50 chance each time of being the positive so I reckon they're wearing down at the same rate.
Some people say that it does turn to silver chloride in the stomach & some say otherwise, I'm not really bothered as it works anyway & I havn't got agyria.