Do high and narrow seat and back bending provide good bike riding posture?
You don't have to do any of these things to commute. If you value safety over speed I'd recommend a more upright bike (Dutch style) which
helps improve visibility and makes it easier to look around. They also allow you to ride in the clothes you want to wear at your destination. What you call old-school is current every-day practice in a lot of Europe.

You could lower your saddle so your feet can touch the floor but this isn't an ideal riding position usually. What would be more ideal is learning how to stop and set-off properly. You need to hop out of your saddle as you come to a stop and put your non-dominant foot down. Then use your dominant foot to put its pedal near to front and top of the stroke. When you set off you push down with your dominant foot on the pedal and at the same time lift yourself back into the saddle.

The saddle should support your sit-bones (at the bottom of the pelvis) which in men aren't all that far apart, hence the narrow saddles you see. However a hunched over riding position also means less weight is put on the saddle and more on the hands and feet than when using a more upright bike. Wider saddles can be more comfortable when you have more weight on the saddle but can be detrimental on longer rides. Your saddle type may depend on your commute length. Generally cheaper squidgy saddles are made to entice people by looking comfortable but are actually worse than a firmer, narrower saddle which is designed to support your sit bones properly.


You also mention riding in the debris-strewn area of the road. Another advantage of Dutch bikes is that they're designed to be robust, with heavier, wider, reinforced tyres.
I would recommend looking into various techniques for positioning yourself in the road, but I can't offer advice on the US since the streets are designed very differently from Europe. Hopefully there are US-specific resources out there.
Edit: I forgot to mention mirrors. I recently changed bike and my new one came with a mirror mounted on the end of the handlebars. It's helped enormously with being aware of my surroundings and traffic, so I'd thoroughly recommend one. Presumably a helmet-mounted mirror would be the same.