Sagging in cab-over bed area -> how bad is this?

Well, it looks like we got what we paid for. We are going to take a road trip south of the border for a few months and wanted to buy an older, cheap TC for the trip. Since we're TC newbies, we're now finding out what can go wrong when you buy one of those ...

As usual, the seller answered a firm 'no' on my question if it had any water leaks or rot.
Now that I'm preparing the TC here for the trip, I noticed the carpet in the cab-over bed looks pretty new ... too new to be original. I pulled it up and found a lot of paper-thin particle board, however, I don't think it's rotten (with my extremely limited knowledge). I pulled up some of the particle board and saw the original 'real' wooden pieces underneath which I also don't think are rotten.

However, see the attached picture: it shows the cab-over area sagging in the middle. Some of the screws in the center seem are loose and I can basically push them back into the camper with my finger.

In light of our upcoming 3 month trip ... what is my best option?

1) ignore this, you won't fall through the floor when sleeping

or

2) this is bad: the supporting wood floor is probably rotten and you need to replace this immediately

or

3) it's OK, just screw some bigger screws in the middle seem to hold it together and put some caulking on the seem

Thanks :)