I feel like this is a two part questions. One part gear, the other part technique.
As far as gear, I think the most important step is to size down. A 185 ski for someone that is 5' 10" is far from optimal in my opinion. Since you seem to be having a little bit of trouble in the bumps, a shorter ski will definitely help a lot, thought you might feel a little less comfortable on the groomers (I don't think it will be that noticeable). Look at the 177 cm Cochise. As far as mounting points, I don't have a whole lot of experience in changing that up, but it sounds like wasatchback's advice makes sense. Maybe a little less drastic than 2-2.5 cm forward, I might recommend 1-2 cm forward. Lastly, detuning parts of the edges is a great idea and will make your skiing smoother in variable conditions and bumps. Follow wasatchback's advice and detune 8" from the tail (or have a ski tech do it for you).
Now as far as technique. You said that you have trouble in bumps and tighter terrain. I would recommend working on two things: edge control and flexion/extension. When you are skiing bumps, it is very important to have control over how much your edges are sliding and where they take you. A good drill to work on edge control is flat spins. Get on a green slope and start turning to the left until you face uphill. Look straight ahead and make sure your edges are in a neutral position (perfectly flat on the snow), and then look over your left shoulder until your skis are facing downhill again. Repeat this in both directions. Eventually, you will be able to do this very smoothly. On flexion/extension: when you are skiing variable conditions and bumps, you have to actively use your knees. You flex your knees when you go over a bump, and you extend your knees when you are over the bump. The ultimate goal is to keep your head perfectly still (watch this video: http://www.youtube.com/watch?v=Y9XYnXXXelA). To begin working on this, head over to a mogul run. Start traversing across the run and try your best to keep your head still (you can image there is a glass ceiling above you that you don't want to break). As you begin getting more and more comfortable with this idea, start taking a steeper and steeper traverse until you are skiing wide, comfortable turns. Once you are comfortable with these turns, start experimenting with short radius turns sliding into the top of the mogul and skiing over it. Remember to absorb the bumps as you hit them. This idea translates to variable conditions too, don't forget that.