1) When it comes to removing sand-textured paint, there are sadly only two options I know of. You can dissolve it with a paint striper (a nasty and dangerous chemical) or abrade it ( which is a nice way of saying you have to sand or scrape it off). I imagine you would want to do a combination of the two. Look for an environmentally friendly paint stripper. There are some that are citrus-based that aren’t too bad. If these work at all, have at it. Soak the paint and strip off as much as you can with a putty knife. Whatever stays will have to be sanded off with a small power sander. Make sure to protect yourself and your home from the chemicals and the dust--googles and a mask are a MUST.
#2 The easiest way to make the oak finish more uniform is to stain the lighter oak darker to see if you can blend it to achieve the darker finish. We do this quite frequently with good results. Lightly rub the cabinets with very fine steel wool and mineral spirits to make sure they are clean. Apply the darker finish (I like to use gel stains for this) with a natural bristle brush and seal the cabiets when you are done with a polyurethane.
#3 As with any small space, try to take advantage of all of the space. There is some excellent stuff out their these days to help you get more storage. There are cool caddies that sit on the floor and then extend over the toilet, making it easier to access this wall space. Also take a look at some hotel style towel racks and bars. These let you store more things out in the open, but in a more presentable way.