Tom,
You have a lot of questions, Ill try and answer the ones that I have experience with and have some understanding of:
#1) Feed chicken parts: Sorry, have NEVER done it and dont intend to start. Salmonella comes to mind. There are people on this forum that do feed chicken parts, and with good results. Just not me. Id rather fry it up for myself!
or bake it 
#2) Feeding to large a food item and then having it cause the snake illness or death: Feeding DRYS ANY really large food items is ALWAYS a mistake in my opinion. Their mouths are SMALL and fairly NARROW and not set up to accept large jumbo meals. having said that, if you do feed large rats or other large rodents to your Drys, the likelyhood that they will regurge is increased. If temperatures are NOT optimal, the snake may just shut down, and go into a semi hibernation state, with the lovely meal of undigested JUMBO RAT in its gut.Which will rot, and potentially kill your DRYMARCHON.A fellow Drymarchon keeper had it happen to him many years ago, and he lost his nice male Yellowtail because of the food/temp. Yes...generally speaking, they will regurge when the temps are either to cold or to hot, but it ISNT guaranteed. I have also found that excessive feeding of small food items(Feeding until the snake is virtually overfull, can lead to the death of the serpent. Temps play a crucial role, but these snakes just arent set up to accept large food items or to be way overfed.
#3) FUR being hard on a Drys Digestive system: MOST Dry keepers feed their snakes either fresh killed or frozen thawed mice or rats. It is a convenient food item that can be purchased relatively easy on line or locally. Personally I think that the hair isnt that good for them, and have had better growth results feeding either rat pups or hairless rats. But THATS in an ideal world, generally speaking rats and mice work as long as they are supplemented by fish, occasional amphibians(frozen/thawed) and vitamin/mineral supplementation.
#4) GOLDFISH- I have used these to start off new neonates on. They seem to work well. They stink and move around alot, which stimulates feeding. The feeder goldfish that you find in petshops are chock full of parasites and usually sick as a dog, feeding them a diet exclusively composed of that causes a thiamine deficiancy. A much better bet would be minnows bought from a bait store. For your Pipa-Pipe, minnows would be a safer choice.
#5) Feeding an Indigo tunafish from a can is an INCOMPLETE diet, as it only is a PORTION of the fish and not the entrails, brain or spine(Calcium) Ive never fed any tuna to Indigos so cant comment on your friends expereince. Tuna is for Tuna Fish Sandwiches..period
Hope this helped. Have a great X-Mas and New Year.
Sincerely,
Fred Albury
P.S.
I dont recommend roadkill food items either. Why waste a perfectly good possum?