Agent Trainer, option mods folder.
Not really, play on lowest graphics with as few girls as possible is all I can suggest. Thank Illusion for the terrible optimization that causes this on even high end machines.
No need, there is an option in the middle bottom of the screen, you can select either cumming individually or together.
They actually can look after themselves and they are intended to start out unable to. It takes a very long time unless you teach them by doing things while they follow you. All medicines are created at the green medicine table, which you place in housing mode. To activate housing mode, interact with the sign posts in certain areas. Also, sicknesses take a very long time to cure on their own, so they will go away eventually, but most likely at the cost of the girl passing out or equivalent effect depending on the sickness. Giving a girl an item will NOT make them use it, you have to put it in the storage of the furniture they cook at, the small fire is the exceeption as it has no storage. None of what you encountered is bugged, you just aren't doing it right. Don't worry, pretty much nobody was at first. My very first playthrough was exactly like you're describing and I had to follow my girl constantly because she collapsed so much. There is an official translation, by the way. I think R4.1 has the official translation natively applied instead of needing a patch, but I will link it, you have 12 hours to download.
Workupload
Yes, it really is pretty good in comparison to previous Illusion titles, not the best, but good.
Yeah, don't use the current version, wait until the dev fixes it, then use the next version.