I have very little in depth knowledge of silver water , but I do know that many years ago it was popular for antibiotic use as well as wound care. There are current topical wound creams etc that have some silver in them. I discourage ingesting this silver compound becase there are known toxicities related to ingestion of silver, especially over the long term(liver, kidney damage, changes in skin color etc.)
I am concerned about this non-healing foot ulcer. In diabetics, wounds heal very slowly, or not at all, because of poor glucose control as well as poor blood flow. Your husband is at high risk for another amputation unless very aggressive care is taken of his toes/foot. Please seek out a wound specialist as well as a vascular surgeon as soon as possible to have this evaluated and treated appropriately so that hopefully you can avoid any further surgeries or amputations. And be sure to keep very tight glucose control as this helps wound healing also.