I'm going through something similar. I decided that after everything that went down in the world, and still happening here in Brazil, it's time I take a shot at making games, since that's the only reason I started programming in the first place.
So, from your list, from personal experience and from reading/watching blogs and gdc stuff, I would say that for an indie studio, your item number 3 is actually the number 1, big number one.
Building an audience is the most important part. I don't know you personal financial situation and how things are on your country when it comes to open a company, but here (and talking about my experience) the first thing I intend to do is to open a small IT dev company, so I can get some money flowing and invest it on my game project, while keeping my main job, because I can't go on without a secured income for people depends on me.
So, apparently, the easiest way to improve your chances of success, is to build an audience from the get go, and grow it while your project is being made.

I would like to start a software dev company as well. Making desktop apps and perhaps small games. I don't have any capital to do so though, so I will have to find a source of income or funding first.

I don't know if this will help or hurt, but for what it's worth, the project I currently work on attributes a significantly larger chunk of engagement to its email newsletter than I originally expected. So while you or I (or even your target audience) might consider the ol' “sign up for our newsletter” prompt annoying, it apparently remains an effective technique in the world at large.

Also, content is king. The aforementioned project continues to receive new features and shiny things, but survey after survey shows that ~90% of what people “care about” is content.

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That's fantastic, thank you. I definitely am looking to the dthompson as a sort-of model for how this could potentially unfold in the initial stages.

At this time I have 3 "probe games" that have surfaced as viable options.

The initial probe game looks like it is really likely to be successful, we feel very strongly about it, but we quickly pivoted away from it because the concept proved to be better than we imagined, and as such began to require a lot of story, world-building, and character design to augment it to its full potential. Also, as it developed we realized it has the potential to appeal to a wide audience, but was still more niche and I'm not comfortable starting out with a targeted audience this early.

About a month before KrampusHack, we pivoted to "CubeShooter" (development name), which is a StarFox-like game. What we found while working on it, is that this prototype had a significantly faster workflow for designing levels and world-building, and, the gameplay is substantially more visual, meaning it would potentially get more eyes and more users drawn in to bootstrap the studio. So for now, the first game has been sidelined even though it has a much better chance of broad appeal and my team-mate and I decided to pivot here just for the purposes of the quick release.

And lastly, there's now the KrampusHack game KrampusReturns, which expanded the availability of tile-based gameplay and pixel art animation, opening up a (yet unexplored) possibility that the work done here could be leveraged quickly into a more substantial game.

2 people. Just myself as a developer (and all the other things) and a partner who's an advisor and design consultant. There's a third person that I have an eye on to do some design and modeling.

Also, ChatGPT joined the team about a week ago.

I hear that. Trimming things down to simplest possible form seems bland and mundane, but in the end it actually cleans things up and clarifies the actual game.

I saw a post yesterday about a team that had to abandon a game a year or so in because "it wasn't fun to play". They had tried to mix team fortress 2 and a rhythm game, which, kinda cancels each other out? Apparently they weren't honest enough with each other to realize that, and, after one of the designers left the team they gave a scathing review saying it didn't even make any sense. The players just end up clicking the left mouse button repeatedly and that's it. What a nightmare to have walked down a road like that and wasted so much time.