I'm pretty much your same stats. 5'9 180lbs. I use a size 9.5-10 boot.
Out of your list, I have not ridden the Phoenix.
I own the 2011 K2 Turbo Dream 156. I would personally cross the TD off my list. The Skate Banana and Raygun are both better for park because they are softer. I would choose the TD for jumps though. Also keep in mind that the TD is the fastest board out of those. If you're into speed, this board rips.
For hardpack/icey conditions, the Raygun gets noisy and washy. The TD does well though thanks to its Harshmellow dampening tech. The Skate Banana is the best board for this condition. The magnetraction works really well on those conditions. Some people find it to be grabby and if you feel the same way, you can use and edge tool and go over the edges. You'll still get the edge hold on hardpack/ice without the grabby feel on softer conditions.
Given that you want to learn park and ride on cruddy conditions, I would recommend the Skate Banana out of your list. It is a mid flex true twin with rocker which is ideal for freestyle. The magnetraction, as mentioned, is going to help you ride on the hardpack/ice.
Sizing-wise, the 156 is fine. Don't worry too much about length. One board's 158 could be another's 156. Yes, the less board you have, the more control you'll experience. However, you will usually be sacrificing speed and stability. In all honesty, unless you are sizing down like 3-4cms, weight plays a bigger role. I'd rather be on a lighter 158 than a heavier 156.
By the way, another reason to get the Skate Banana is because you already demoed it and know you love it. Why take the gamble on one you have not demoed?