As for the feeling of loneliness in a room full of people, yep...we have all been there one way or another.
For several months after Ms. Wonka moved out, I recall one event at a theatre and I felt like the walking wounded with a huge gaping wound from a blast in the heart with it's innards hanging out....and the searing loneliness was unbelievably heavy around my shoulders.
Phew! Glad I was able to get past that awful feeling. The loneliness stems from the feeling that your best friend has suddenly went AWOL and you have this knowledge inside you that you just cannot share your day or adventures with your partner.
Yeah, reading your post ^^ brings back those distant memories back to the forefront...like a blast from the past. I now look at it as a phase that I went through and tell myself, "yup, been there...done that" like one recalls the teenage years.