He also seems to own the document processing company.I don't want to go into the nasty details, but he started off as unprofessional and then has devolved into some really psycho behavior, after I gave him some neutrally/professionally-worded feedback that he took personally.

Hire a professional cleaning company (their nose will back up your claim) and try to neutralize it.

@Jerry Puckett Even as a non-refundable deposit, those funds should be held by a neutral third party.

You can get peel and stick wallpaper that might work, but unless it is neutral I wouldn't do it and even then do it with the understanding that it may not hold up well. 

Look around your room and you will see even though the walls are probably painted with one colour, they look a bit different depending how the light is hitting them.If you don't have paint or need to paint all the walls, check the paint store for neutral mistints. 

You could achieve a better return with less passive options like BRRRR, but they take time/effort.I have purchased RE with worse cash flow projections than this property (twice I have purchased properties that were virtually cash flow neutral with my conservative projections). 

This negative position can consume years of cash flow before obtaining a neutral return.  

Paint all rooms and trim a neutral and fresh tone3.

I am an army OEF veteran and the young age of 32 i have lived a life greater than most of those congressmen will ever live in their unmoral lifetime (congressmen is gender neutral BTW.)   

Anyway, I just did a full repaint of the ceiling and baseboards for the first time since construction, as well as taking the walls from mid-aughts-earthtone brown to Navajo White (I'm skipping the greige/gray and going to a more classic neutral because the gray is definitely on the way out by now) and fixed all the little things that were off.