Standardize on sRGB and things will just work, and neither labs nor publications will foobar your files..
Well, that's the MSFT way...and if you do that you are leaving a lot of capture color and thus potentially image quality on the table...
The ProPhoto RGB color space is only a problem to people who don't know how to set up their Photoshop Color Setting policies to "Preserve Embedded Profiles". Which has been the Photoshop default since CS (I think the "North American General Purpose was intro'ed in CS but it could have been CS2).
Then the only question is whether or not you want to use PP RGB as the backbone color space in Photoshop. Many times I'll have my RGB working space set to sRGB particularly if I've doing a lot of book work and need to work with screenshots. Oh, I'll still open images through Camera Raw as PP RGB images in 16 bit...tat is my default for photographic images while working in Photoshop.
I'll also cheerfully suggest you never give ProPhoto RGB files to anybody else. Clients, printers, photo labs, etc. will rarely know what they are doing so at the biggest, I'll give out Adobe RGB or even sRGB if they sound particularly stupid.
For CMYK, going from ProPhoto RGB to CMYK vs. sRGB to CMYK, sorry, big difference and sRGB is substantially inferior in a large number of colors in the CMYK gamut. sRGB is inferior in cyans and blues/greens where it's really tough to get textural detail in those saturated colors. Oddly, it's red and red yellow/orange where sRGB really suffers in conversion from sRGB > CMYK...images whose colors blockup from sRGB maintain far better color gradations coming from PP RGB.
So, if you want the best working space for your hard worked master images that will future proof them for ever expanding gamuts of output color, going sRGB would be very short sighted and very limiting. Which, ironically is one of the big reasons that many photo labs demand sRGB...because they are very short sighted and they want to limit photographers' expectations...
As far as the rest of the 1-4 list...I would also take look at #1. While I agree and use Macs, it's been my experience that in the last few years, Apple (read Steve Jobs and his underlings) have pretty much marginalized ColorSync down to the point where instead of just making things work, it tends to get into everybody's way. The intentionally untagged profile target is just the more recent and obvious issues...print out of Windows is in many respects, easier and less prone to system problems than recent Mac OSs.
The single biggest mountain to climb relating to color management and Photoshop is the creation and proper use of high quality (and very accurate) display profiles. I have no particular problem with any of the hardware/software options out there but I tend to seriously suggest the NEC line of wide gamut display such as the 3090WQXi along with the NEC software and a puck suitable for wide gamut displays...
Sadly, it's the display where many photographers tend to "cheap out" and get lower end solutions that can cause all sorts of problems particularly related to display output. Anybody who complains about "dark prints" is prolly not deploying their display and display color management correctly.
Then, of course, you have the display environment...I have, for a long time, built an optimum imaging environment with reduced brightness, indirect environmental lighting with a D50 white point and no reflections ever on the display screens...I also have a D50 GTI viewing booth as well as a lamp with Solux bulbs and another lamp with straight 3000K lighting. All of which are used for proper viewing and print evaluation...
Hey,it could be worse...it could still be 1995 when none of this stuff worked :~)