There is no capillary break between the porous cement and your flooring. Using 1" XPS first on the cold/damp cement floor followed by your plywood and then flooring would solve your problem. This is also assuming your walls are setup properly, there are no water leaks, humidity not too high...

In early September 2012, a top-rated flooring company which was subcontracted to my general contractor completed installation and finishing of new white oak floors in two upstairs rooms and the downstairs den of our new house. The floors were stained and finished with three coats of Bona High Traffic. Each coat was allowed to dry several days before re-application. They also sanded the existing pine floors in the living room, dining room and hallway, stained them, and finished them with three coats of Bona High Traffic. The floors looked beautiful, but my wife and I immediately noticed a strong odor, despite the insistence of the flooring man and the general contractor that this was a "green" product with no smell. I had been working in the house almost every day for five weeks before the floors went in, and had never smelled this odor before the floor installation. Nonetheless, I tried to believe that perhaps it came from some other source, or that it would go away quickly. Just before we moved in, the house was cleaned and dusted extremely well by a maid service, including removing the covers on the baseboard radiators, and thoroughly vacuuming. Despite all this, after moving in, the odor became more noticeable. My wife and I first thought it might be due to the boxes or dust generated by moving. However, even after we had cleaned up the boxes and vacuumed several times with our excellent Miele vacuum with HEPA filtering, the odor persisted. I tried to think of ways to ascertain whether the smell was coming from the floors or from some other source. After a lot of trial and error, two simple experiments finally convinced me that the source was the floors: First, the smell was only present in the rooms where the floors had been treated. In the kitchen and breezeway, where we eat and sit for long periods, there was no such odor; also not in the basement where I spend time at the workbench. Second, by kneeling down and putting one's nose against the floor, the odor could be intensified. This odor cannot be detected in the kitchen, bathroom, or breeezeway floors where no Bona High Traffic finish was applied. The worst of it is that now, four full months since the application, I wake up every morning with a runny nose and sneezing from the irritation caused by the smell. It is worst in the rooms where the oak was installed. Naturally, it is most offensive in the bedroom where one spends 8 hours every night. By leaving the windows open a few inches with cross ventilation, as I do every night even in the cold, the odor is reduced, but still not completely eliminated. The only good news is that the smell is gradually receding. It is not annoying me anymore in the rooms with the pre-existing pine floors. I'm sure that after some finite amount of time the outgassing will be complete in the oak-floored rooms as well. But how long? It is four months already, and the improvement is very slow. There is no question in my mind that the odor problem comes from the floor treatment. This does not prove that it is the Bona High Traffic by itself. As the floors were also stained, it could be the interaction of the Bona High Traffic finish with the stain. Either way, there is an odor problem with the Bona High Traffic product that has not been forthrightly acknowledged by the manufacturer . The product should be able to be applied in conjunction with stains, and not leave such a persisting odor. It is disconcerting to hear people who have an interest in the matter, such as contractors who use the product, or designers who recommend it, imply that there is no odor problem. This entry is intended to cause them to hesitate before saying, "In so many years of using the product, I never had a complaint." I have suffered the odor problem, and so did two other people on this page. How many more, who haven't troubled to write it up? I think that the company needs to carry out a scientific investigation, and try to determine what is the problem (perhaps an interaction of two products, or of the product with certain woods?). It should be noted that the term "green" or "natural" does not mean odorless. A skunk is natural, but it stinks. So does sewage, or the organic esters that produce the smell of bananas. So let's get real here, acknowledge that this Bona High Traffic product affects at least some people adversely with its persisting odor, and try to get to the bottom of it an honest and scientific fashion. Thank you for hearing me out.

Is it possible to move the door? That would the optimal scenario. A pocket door could help as well, but it still couldn't go wall-to-wall. I've never had problems with sound/privacy with a pocket door. Maybe you could put the vanity towards the back part of the wall, then install some shallow shelves behind the door, so that space isn't empty. Might help balance it a bit. Or a nice, big, heated towel rack :)

You mentioned having a front porch so it sounds like there is space between the (assuming) concrete porch and the foundation that is getting larger and allowing the water to penetrate down the foundation. But that is just my educated guess. Depending on which direction your front door faces, you may be getting the rain directly hitting that side of the house and dripping down. An overhang for your porch may help but I wouldn't completely discount waterproofing companies. We had some water dripping down one of our basement walls and had a couple of companies come out and give us free estimates on how to fix the problem. In our case we had mulch that was covering up the weep holes. We had that fixed, along with a few foundation cracks that happened with normal house settling before we finished the basement.