Xenoestrogen are different than plant estrogens. Generally plant estrogens are called phytoestrogens and they don't all act the same, very different levels of bioavailablity and just how they affect your body in general. Soy is, generally speaking, one of the worst phytoestrogens for you but fucking with hormones is a complex subject.
Xenoestrogens though, there's no getting around those. The only question is which ones have enough of an effect that they're worth taking the effort to avoid. The fact that many of the things in the modern environment have an estrogenic effect on the body has been confirmed many times by now. BPA for example is one of the best studied ones.
mct.aacrjournals.org/content/1/7/515
ncbi.nlm.nih.gov/pubmed/9607780
The long-term effects of xenoestrogens on human males are not well studied unfortunately, probably because there's nobody paying for it. Not many governments or foundations out there funding research on subjects like why modern men are so feminine. There's big money in studying breast cancer though. What we do know though is that xenoestrogens can increase your risk of a number of estrogen sensitive cancers, like breast cancer.
As for the smiling and happiness thing, try it. Force yourself to smile and you'll feel better right away. Try making a range of expression and holding them for a second, and you'll notice they affect your mood correspondingly, if only slightly. Why doesn't this cure depression? Well probably because depression is a more complex issue than just feeling down. Here's a solid article on it before the NYT was trash.
nytimes.com/1989/07/18/science/a-feel-good-theory-a-smile-affects-mood.html?pagewanted=all
Their biggest critique is that the study doesn't sufficiently explain the mechanism of the effect, but it does exist somehow. As for posture affecting your brain chemistry, there's a lot of stuff on that lately. I know a lot of people don't like TED talks here but this was a good one.
ted.com/talks/amy_cuddy_your_body_language_shapes_who_you_are
And again, you can try it yourself. Stand up and take a powerful posture for a minute or two, like a powerful king and you can feel it affect you. Similarly, hunch over in a timid, submissive pose and it will similarly affect your mind. Now the last bit, whether this affects your testosterone levels at all is admittedly pure speculation on my part. But seeing how drastically your posture and facial expression can affect your mood and mindset, it's not far-fetched to believe it may be able to affect your hormones in some way as well.