Current code says: 1. Use 6x6 posts, not 4x4. 2. Don't sandwich beams, either set them on top of the post with a post beam connector, or notch out the posts and set them on top of the horizontal part of the notch. Lots of people made decks in the past (and many probably still do) with sandwiching, but post caps are better.

The post is heavier gauge and has four corners that resist movement. The flimsy-looking cap has no such geometry. If it were me, I'd get some PVC cement or some 2-part epoxy and glue it in place. Tape the corners down to the top of the post with masking tape while the glue sets up.

I don't find this either new nor worthy of thought, it's been long known. I've read that the highest incidence of problems tends to be found in small towns, smaller community hospitals, and larger understaffed public hospitals. A contributing problem is that the medical boards of many states don't allow public access to complaints, investigations, and disciplinary actions against physicians. Such information could be most useful to know which ones to avoid because of past problems. The secrecy is beginning to change in many places due to public pressure for sunshine on these records. The best thing for patients to do isn't to fool themselves into thinking they can become an amateur physician for themselves, that's folly and probably the worst approach. A much better thought is to try to be seen by the best physicians at the best institutions available in one's region and that often means becoming a patient of docs practicing at medical schools. Find great docs, learn from them the wherefores and the whys and then follow their advice. Or don't, that's everyone's choice.

I had a new oak staircase and handrail installed a few years ago. The carpenter used Bona Mega Floor Finish on the stairs and handrail after he stained them. The carpenter I hired, specializes in staircases. He matched the stair stain to our Italian porcelain wood look tile flooring. I am so pleased how it came out! Your staircase is lovely!