Soren, no offense, but I think that was a bit of a massive "duh!" when I specifically referred to smallest waist competition, not much added info for that fyi :-/.
Plenty of guys work out or do sports with binders and can still breathe. The issue with it should be more to do with over heating and range of motion. It's far preferable to work out without a binder, that's why I bought my own weights, but it is possible. One of my mates is a distance runner and he just got back to it following top surgery and says that he loves being free and not constricted. He can run without a shirt now too. But as for breathing, there's not much difference.
There's a tendency for folks to bind super tight and it's overly flat. Guys aren't totally flat, they still have shape, so having a little shape is okay. If you're worried about it, baggier tees or an overshirts will hide things in a safer way than binding so tight you can't breathe properly.
Also, you could try working out. The bigger your arm and shoulder muscles, the more your chest just looks buff.
I guess how folks can cope is that they breathe more from the diaphragm, but it is extremely important to have periods where you aren't binding. Even muscle damage isn't always fixable, and if you have a dent in your side caused by binding, they most likely would do an xray, or at least should. Now that you live alone, try and one up on your dysphoria and continue just wearing a loose bra and put a baggy tee on so you can't notice. Then just maybe a tee by itself at night.
When I refer to watch I don't mean marks from lying, people get them lying on their back. It's caused by the body swelling in certain places at night because of position and temp fluctuations.
If you can't take a deep breath with your chest with a binder, and wear it too long during the day (and night), you also run a high risk of pneumonia and that would mean going a long time with no binding whatsoever! :-/
I find the best way to handle dysphoria is the same way I've handled intense pain with broken bones. I keep telling myself that soon this will be nothing but a memory. I'll look back on it but it will still be over.