Miele Man

I use a KMC 8-speed chain on my 6-cogs equipped bicycles without any problems. I use a quick-link on all my chains never a Shimano chain-pin to join the chain. OOPS! I see you used a quick-link. I don't know why you had to use pliers to join that quick-link. I've never had t o do that.

If the smallest cog on your bicycle screws on then it's a Uniglide cogset. Unless it's a freewheel and not a cassette.

You said: "I tried using tools to even out chain but could not eliminate rub on rear cage, near first quick link rivet and then later also around 2 rivets further..."

I'm confused as to what exactly you did there. Do you have tight links on t he chain?

You also stated: "but interestingly seems both shift cables get affixed to shifters at a time, there appearing to be one screw securing both shifters, or very nearly."

Are your shift levers mounted on the SIDES of the downtube? It almost sounds as though you have unusual shifters perhaps mounted on top of the downtube. Would you post an image of your shifters and also an image of your front derailleur and chain running through it?

Cheers