The StarSan turning milky doesn't mean your fermenter is harboring an infection.
I'm still not convinced infection is your problem. It may be. It may not be. It may be part of a multiple-issue ordeal. The way to get to the bottom of it is to be methodical in your approach. Make a simple brew with new yeast and don't take samples until it has had a couple weeks to sit in the fermenter. You could also make a small batch in a one gallon glass wine jug at the same time, and see if that batch takes on the same flavor. If the bigger batch is the only one that tastes off, you are beginning to hone in on the problem. If they both taste the same, you know the issue isn't the fermenter.
If both batches taste fine, you are back to the yeast being the likely source of contamination. You can keep testing, changing one variable at a time, or you can move ahead with whatever new process first produces a beer without the flavors you are working to avoid.
If you take a sample on day 4 (don't!), it won't taste like the beer it wants to become. Resist the temptation. And for the love of everything holy, don't deem the beer an infected loss if for some reason your will power fails you and you taste the beer early!