Re: 4K version
Based on what I've just read on Discord, someone from the Eternumite tier can request for 4K renders of any still image in the game. However, said someone mentioned that Cari limits those to 2 images per month, which sounds weird if he has those uncompressed images somewhere and he simply just has to send those upon request.
Unless (and this is just guesswork on my part), in order to save drive space, he no longer has those uncompressed images but he still has the scene data saved so he can go back to it and rerender an image if needed/upon request. If so, then it's also likely that he doesn't have the uncompressed videos for the animated lewds, meaning if he wants those 4k videos then he'll have to either upscale the existing videos or rerender them again if he has the scene data.
Assuming what I've said above is true, then I can see it being another reason why he doesn't want to bother with doing a 4K version of the game, especially when doing so would prevent him from working on new stuff (like, say, his 3rd game).