1-Brakes that seem to hold on too long: This sounds like you are using a time-based brake controller. The way these controllers work is you step on the TV brakes and a few seconds later the trailer brakes engage. you release the TV brakes and a few seconds later the trailer brakes release. That 2nd delay is what you are experiencing. My experience has been that if you change to a proportional brake controller (tekonsha prodigy 2) you will eliminate this affect as the brake controller works based on the inertia of the vehicle vs time of your foot on the pedal.
2=Noisey water pump: this too is common. Your choices to cure this problem are A)isolate the pump from the camper (ie thick foam rubber or the like) B) isolate the vibrating pipes from the camper (foam wrap) C)install an accumulator tank (http://www.amazon.com/SHURFLO-181-20...ywords=shurflo
). I have tried the extra hose kit from SHURFLo and I cant seem to make it stop the noise.
3-Lights dimming: I have had this on and off too. I think it is related to a batter that is not fully charged (even when plugged in to shore power). Recall that the battery acts as a storage reservoir for 12v power. Some battery charger/power converter units require more battery capacity than others to operate the 12v systems in the RV. If your battery is old and does not have sufficient capacity then you get the shuttering 12v lights when operating a high demand appliance.
4-Black Tank valve: the valve is an easy job to replace. the parts are inexpensive and the job is quick. The part that is difficult about changing valves is A) getting to the valve (ie, it may be in some obscure place) and/or B)having waste left in the tank that you have to deal with when opening up the valve housing. Also, make sure you get the correct diameter valve. an example: http://www.amazon.com/Valterra-T1003...rv+waste+valve
ALso, if you have a sticky valve, I have had good luck using COCO lube from Camco. Regular use makes your valve operate smoother.
5-Tow mode: Mainstream thinking is that if your transmission is not constantly shifting up/down then tow haul mode is not required. However, my truck's tow/haul mode does more than just monitor the shifting it also looks at how much I am braking and downshifts to help me slow, etc. So I would encourage you to review your TV manual and/or research the forums for your truck to see others experience with it on or off. I have not experienced the situation you outlined unless going up an incline (could be a very slight incline in my TV).
Welcome aboard and hope you enjoy your rig in good health!