I cannot help you on the DIY beer line cleaner question, but I can say that bleach (or anything with free chlorides) will pit/corrode most stainless steels, especially 304 and 316 grade.
Im not sure what you mean by leaving the regulator open. This is a way to carbonate your beer. Leaving the reg opened to 12 psi for about a week (depending on temperature) will result in your beer having carbonation. If you could restate that part of the question, I'm sure I could be more helpful.