Is the steerer tube of that fork carbon (since you mention an expander plug, I am guessing so... usually aluminum steerers would use a star nut)? If so, stop what you are doing and make sure you have all the proper supplies. Before messing with carbon parts, make sure you have a torque wrench and carbon paste. There's simply no way to tell by hand what 9nm really is... and if you miss on either side, bad things can happen. Carbon paste (or assembly compound) is grease with pieces of special grit suspended inside. This keeps the parts from freezing together over time, and also increases the friction between the parts (so a stem holds the steerer better at the same torque than it otherwise would).

I think your problem is simply not having the proper tools to assemble this. With assembly compound and a torque wrench it should go together nicely, and without those things you are risking your $2,000+ investment (and your health in the case of catastrophic failure). These tools could be bought for less than $100 and are great investments for anyone dealing with carbon.

If your steerer is aluminum you have a little more leeway, but I would still take it in to your LBS to get it looked at. Better safe than sorry.