For my convinience, I will refer to all elements making up an unit as "modules". So all the techs, population, structures and what not that was used to create the unit in the end will be called modules in my questions
Most of those questions could be just answered by experimentation, but I've got limiter resources and time, so asking will be more efficient.

1. Do resource-generating structures (powerplants, farms, quarries and mines) need to be placed next to an outpost/town/city/other structures or can they be build over any hex?

2. I've done some number-crunching over the thread. Broadly speaking, each module more or less corresponds to +.2 bonus. Is that right?

3. Each unit can have either 2 or 3 modules (so +.6) before the upkeep will start to increase accordingly.

4. Units can thus still qualify as militia (no upkeep) as long as they are no more than +.6. Is that correct?

5. My eccentricity, ['Free' Army], says "though monetary upkeep for armies is nearly nonexistant". I know this can be easily balanced out by giving me some shitty food/power/fuel upkeep out of nowhere, but assuming main issue with upkeep is currency-based - does it mean my militia can have more than just +.6 to still be treated as militia?

6. Or does it actually means my units in general act like militia, upkeep-wise? (I don't believe I could get a bonus this powerful... or I was playing my nation completely wrong from the very start, which is downright scary)

Now assuming my entire conclusion with modules and their +.2 bonus per module was right:

7. When upkeep is calculated, it's done based on modules. So is using higher tech levels (eg Infantry II) count as if using two modules or just one for the purpose of the upkeep? Surely higher tech will provide higher bonus in the final calculation, but what about upkeep? Thus the final question no. 7 is: Is higher level of technology more-cost efficient or makes no difference for the upkeep calculation?

8. Population can be used to strengthen units during production. At what ratio?

9. How does that ratio affect upkeep? The same as standard per-module-increase or some separate counter?

10. Early on, Jeep was eating out Oil, then it was converted into Recon Rover Rick and it stopped. Then I've got Biofuel tech. Does it mean I'm free from fuel upkeep, at least for non-[Heavy] vehicles?

In short - is Free Army crunch-wise more like Spartan Federation from Alpha Centauri (hard to kick-start, but impossible to stop juggernaut) or rather United Citizen Federation from Starship Troopers films (inefficient and wasteful grinder that barely holds together)?