Stan,
I'll try and answer your questions as best I can,
1. Operating British Sea Kings in hot and high conditions we generally try and fly with Tqs matched. If the engines are poorly matched in terms of NG or PTIT (T5) we will match those so that we are getting the most out of the engines. If matching by something else generally accept no more than 20% Tq mismatch. (Westlands reckon you can go upto 30%) The only problem with this is when operating at the top end of Tq it becomes increasingly easy to inadvertently Overtorque. (Our limit is 111% Tq twin matched which becomes quite hard maths when you have up to a 30% Tq mismatch trying to get a heavy cab out of a dusty LS)
2. Taking off the Rotor brake should generally be a gentle movement. (Just being gentle to the moving parts), we pre torque the head to 70% NG and then release the brake. Single engine Flight Drive starts are reserved for last ditch attempts to get us out of holes that we would rather not spend the night. Don't forget though that effectively you are only single engine when in Accessory Drive even with both engines running, only one is providing a direct drive to the Gear Box.
3. You should avoid landing with the Tail Wheel lock disengaged as it can cause all sorts of grief particularly when trying to deal with other problems. It could lead to rolling if any pedal is left in during a running landing, crosswind or brakes jamming etc. Best not to tempt fate on that one. With emergencies such as Tail Rotor Failure the locked Tail Wheel helps straighten the aircraft as it touches down, if it was left unlocked you could end up in any odd position including upside down as the main gear touches down.
4. The AFCS should be out for all stages of ground taxiing and fueling. Occasionally when in a FOB we leave the AFCS engaged in case we need to get out in a hurry when loading/unloading pax. There have been instances of ASE packs that are approaching the end of their life causing the aircraft to spin on the spot when AFCS is left engaged and the pedals are left unguarded. Thankfully the fuel crew managed to get out of the way.
5. Your minimum Tq during descent should be 10%, the reason being: If you allow the gearbox to freewheel during the descent the engine failure will not be as obvious until you pull in the lever at the bottom (No matter how gently you do it that Tq just won't come back up). If you have at least 10% Tq on you will notice that you get a Tq split and know that you have a problem. If the inputs start whining it could be a sign that they are starting to wear out/vibrate dangerously.
Hope this answers your questions, some of the best flying I've had was in the Stan particularly during the summer months, if you're not sure how the King will fly you will certainly find out from May onwards.