9.3 is severely outdated and doesn't have a lot of the official content released, I would suggest RX4.1. I'm not even sure Kplug 1.9 has the shower sex in yet and I don't know if newer versions of Kplug are compatible with versions of the repack as old as 9.3. It is in optional mods in any version of the repack, though.
And if they do it in the storage room, forget it. You're instantly in a line of sight the second you start walking.
No, not creating an editing program, using ones already made to get to the lines that need to be changed and then reversing what I did to get to those lines to make the files usable by the game again.
I'm not sure you can, but it might be possible. Yeah, Kplug is one of the most extensive mods I have ever seen for a game by Illusion, Katarsys is doing a great job with it. I do wish the journal feature had a few more details that are hidden, though, like the number of dates you've been on with a girl. That would really help me keep track of who is up to the point of being able to select a date location and who is completely maxed out. I'm trying to get them done as quickly as possible so I can phase in the next group of girls, which is the 15 default slots for other classes, then move on to increasing those classes to 25 each. To do that, I need to spend as little time on each as necessary. That means talking to them as few times as possible while maxing affection and H desire, getting their H stats done in as few H sessions as possible, and going on as few dates as possible to get them to the mock wedding.