All of the tongue weights listed seem to be on the lite side. You need 10-12% of the gross on the tongue. A lite tongue will cause sway. I agree that you have 900 lbs available for your load. Give this site a read.
http://www.sherline.com/lmbook.htm
A WD hitch will shift a percentage of the tongue weight to the front axle and some back onto the TT's axles. Being near the max ratings is going to require you to do some research to get your trucks limits. Once your armed with the specs it will help eliminate rigs that you know won't meet your needs. Get a good WD hitch with built in sway control.
One major thing I took away from your problem is that you haven't yet decided exactly on what you want. Planning to keep the rig through the ownership of this truck and into the next means a long term commitment. This would require that you find a floorplan that your happy with. You need to sit down and make a list of what you want and things you don't want. Don't settle for something you don't like, keep looking. The rig you want is out there, you just have to find it.
Your money ahead of others that bought a rig and then had to upgrade this or that because they didn't check things before hand. Good luck finding that perfect combo. I see many happy memories awaiting you.