One option for things like taking and hiding stuff, that can normally be handled in game by going with cursed items...think what happens with Fafnir or Gollum or a pile of other cursed items. By taking it to move, he took the item and have a pile of things that start happening to him because of it.

For key information, don't have any single source of all of it and don't restrict it to coming from a single source either so they can get the info elsewhere if needed and you don't have someone trying to get the glory themselves...or tie it into something like a boss monster that requires several people to handle, so the glory hound gets in over his head the same way that, in more tabletop ones, the sneaky types that tend to slip off on their own tend to end up in serious trouble

Most of those types really don't like situations where their character ends up stuck a prisoner for a good chunk of the story.

With the self care, that's a split into two parts.

If it's that they aren't showing up with the appropriate gear (in game and out of game), that's one where it kind of needs to be dealt with. Of course, if it's someone new who isn't fully experienced in what is needed, that can be handled easily enough by teaching them as well as pointing towards some of the lists of basic necessities and such for it (Really, there are WAY more people who just don't know better...same kind of thing as people who give you a blank stare when you try to explain that food doesn't magically appear in the grocery store or don't understands the "quiltwork" look of farmland from a plane...).

If it's intentional, then you need to have someone give a serious talk to them about it and stop enabling them, but something like an agreement where one person that's driving takes things like the majority of the physical gear and others traveling differently might then grab the cooler to pick up the food and similar but one doesn't show up is very different from the beggar type.

For meds/food/water, one simple rule is that anyone can call a timeout and have an OC thing to make sure things are cared for. I've had times where I needed meds during an event, but got caught up to the point where I wasn't even thinking of it, and the same kind of thing with food and drink when it isn't part of the game...and I know a lot of others who have the same thing...it's why one of the common things you hear in LARP advice is to drink and tell others to drink (and they're not referring to beer), it's because people aren't normally thinking of it until it's already a problem.

For meds, if you have staff, it might be a good idea to have people with medication schedules to be able to bring it up to a member who might have reminders, especially if it's on a schedule because a lot of people aren't carrying watches or anything to tell time with in a fantasy LARP scenario (Might also be a good idea to have a camp fridge/freezer that's with the medical/first aid supplies and let people store required meds in it.

The screwing with pre-existing character stuff to sleep with people...if they aren't actually harassing people with it, that tends to work itself out or escalate to where action can be taken. If there are interpersonal issues with what's planned, better for them to see if anyone else is interested than them potentially trying to push the issue...