Well, in the mean time, I did not bother experimenting with EX-5. Didn't feel in the mood for that as it's too tedious. Instead, I decided to experiment with the impregnation and birth mechanic using the slimes in the 3 area. Specifically 3-6, but as far as I can tell it doesn't make any difference. They're obviously useful because they can assault the heroine even without her losing all her health, which makes them very convenient.
Now, one thing to note is that the sprite or the zoomed in image do NOT update during sex if she becomes pregnant... however, if you press Q and open the menu, which is available while she's getting fucked and First Aid or Quit are not options, this displays her status.
From my experiments so far, even when starting with the base 10% impregnation chance, it generally doesn't take more than ~6 minutes at worst until she gets fertilized. If you're lucky, it'll happen the first time the Semen status is applied to her. Hell, it can happen with the left over semen status from a previous run when you enter the stage, AFTER she gave birth... though that's pretty rare.
As far as I can tell, as long as she has the semen status, the game rolls for fertilization, though I don't know how often that is.
The important bit is that you can just leave her on the slime and she'll get fertilized eventually.
Once "Fertilization" status happens, it takes ~1 minute until she transitions to pregnant status.
At "Pregnant" status, it takes ~5 minutes until she reaches labor pains status. At this point, you can quit from the stage using the Q menu, have her give birth, then rinse and repeat.
Fastest cycle is probably around ~7 minutes. Slowest is generally around ~12 minutes. I recommend AFK farming with 15 minutes intervals. Get her in the stage, set her on the first slime, do something else while the game runs in the background, come back, check if she's in labor, which she will be, quit, birth, rinse and repeat as often as you like while you do other things.
Other things of note:
-Rarity seems to be completely random. I've gotten everything from Normal to UR from births, albeit the latter was exactly one time. If there's anything that affects the quality of the chip, I can't tell what it is.
-Double Egg Birth. Still no idea what triggers this. I thought that it was time spent in labor pains even after the basic pregnancy is over, but if that is it, it's longer than 10 minutes I think... No idea HOW long, or if it even is that. Either way, if it's time, it's long enough that you lose out more trying for double-eggs than just faster cycles. Well. Unless you're busy and can't check on her every 15 minutes. In that case, 30 minutes might guarantee double egg? 40? No idea. Gave up on figuring it out especially since it popped up randomly at times in way shorter intervals. Maybe it's completely random too.
-Time for sexual status effects does NOT pass while in the Menu. That means pregnancy does not advance in the Menu. Only in stages. Which means she HAS to be at the labor pains stage if you want her to give birth when she gets back.
-Supposedly, labor pains reduces movement speed. Either this is bugged, or the effect is low enough that it doesn't matter in most circumstances.