Think the file is GalaxyDefs but if you do a search in the steam directory for Insane you should find the file. I believe the habitable planets is a percentage of all planets. 

As with all mods the answer is, try it. If you are a founder you can correct your name by opening a ticket with Stardock. I think the list is just founder elites...could be wrong about that. 

Lol think I was replying to something else I donno. Lol copy the file to the mod folder and then edit via notepadd (or notepad++). I usually take the safe route myself and make all changes a mod.

You could also take a look at this thread:

https://forums.galciv3.com/465933

They are talking about custom map sizes but a portion of it seems to affect the general outcome of total creation of planets and habitable and everything else but my post above should represent the percentage of total planets that would be habitable as far as I can tell. I don't delve too much into xml, just enough for my personal changes.

I made a new group that fits between Rare and Uncommon, adding the entry into both MapSetupDefs.xml and GameSetupDefs.xml, but the option, called "Sporadic", doesn't show up ingame. Any tips on why that's the case? Here's the download for it, if you want to take a crack.

Well in the current file the progression is:

Rare 0.1

Uncommon 0.25

Occasional 0.3

Common 0.4

Abundant 0.5

This is why I thought uncommon should be 0.2 but if you wanted to try half which I actually thought you might that would be 0.175 so here:

https://www.dropbox.com/sh/2tmmcsu3ipqu3q0/AAB5ZUVCwepxUFPcd7_N7ueza?dl=1

unzip this to your mod folder and should work on new games

if you want to edit it yourself just find

<MapSetup>
        <InternalName>Uncommon</InternalName>
        <Stars>0.65</Stars>
        <PlanetFrequencyExp>1.5</PlanetFrequencyExp>
        <HabitablePlanets>0.175</HabitablePlanets>

and change the 0.175 how you wish, hopefully you can get it where you like, good luck

@Lavo_2 i would but that's outside of my ability, the fact that they have a Habitable Planets tag in mapsetupdefs.xml for None surprised me since it isn't a selectable option so you might be out of luck that it could be internal code. That's my best guess which sometimes isn't worth much

You might be able to fix it in some ways by lowering habitable worlds to rare, and cranking extreme worlds up to abundant. While they would still be obtainable it would be quite a while in game before colonization of those worlds could begin. While not a true solution, it may give you something closer to what you are looking for. It also seems to me it might even fit well with your idea of few habitable planets. Since the others need alot of work to be "habitable."

dragoaskani's idea isn't bad, i was wondering how extreme factors into total planets and habitable. Is it a % of total for both or are extreme a % of habitable? I assume the latter but have left extremes low or off for most of my games. Looking at the xml numbers most likely % of habitable, still would like an opinion of one who plays with them a bit