Each season will be sold as an independent game (that will force me to add a questionnaire to Season 3

).
Why? Because devs who know about this better than me say it's the way to do it. DLCs for adult games have a selling ratio of 10-35% with respect to the original game. Seasons as "Independent games" have a ratio of 60-90% and even push the sales of previous seasons a bit. That's because (among other reasons) Steam doesn't advertise DLCs. I don't know if I will sell zero, 1, 100, or 100,000 copies of Season 1, but giving up 25-80% of those sales for Season 2 (I think Season 2 is better than Season 1) isn't a good perspective. And it would be even worse for Seasons 3, 4, etc.
Let's go nerdy (and optimistic) and think Season 1 will sell 1,000 games, and use the average retention is 22.5% for DLCs and 75% for independent games for the math.
As you can see, Seasons 4 and 5 would only report losses after Steam cuts and fees. The totals would be 1,290 sales with DLCs and 3,051 with independent games. In neither case will I become rich, it isn't the goal, but doing it as DLC doesn't make any sense.