Hi Sly, sorry to hear your woes.
I can't say I have years of experience with these models and I am sure lots of guys will come on after me to add their wisdom but from other experience I do have with mechanical drives and chains in particular I'll give you my opinion for what its worth so here goes:
1) I think you meant 'Renold' and yes they are still going as an international company of some repute. I would have no problem fitting their product on my bike. (Reynolds were the old Ti company that is also still out there I believe, famous for race winning double butted cycle tube sets such as Reynolds 531 and probably supplied BSA in their day)
2) Obviously a lot depends on how you drive it but a properly set up, well lubricated chain running in a closed environment such as our primary drives should be capable of at least three times the mileage you have done on yours I would expect.
3 & 4) There really shouldn't be any great difference between any of the well known chain suppliers. I fitted a Regina branded chain recently from Feked in UK which comes with the joining link but only because that was the one they were selling! (Regina are Italian so it makes my bike go faster of course)
The technology is very mature and I would be very surprised if there was a quality issue with the chain at the root of your problem (not impossible however).
I my view nothing wears a new chain out quicker than fitting it to old worn sprockets. It is always best to fit new chain and sprockets together. If this proves uneconomic then the next best thing is to change the chain way before it is worn out and in this way you will prolong the life of the sprockets. Chain is cheap, sprockets not so much.
If the alignment is OK (and mine wasn't!) then the question becomes one of lubrication and tension. There are those who say primary drives can be run without oil. My view is lube makes everything better! Tension remains as the most likely problem then and for my money I would always err on the side of running slack rather than running too tight.
There should be at least 1/2" of up and down movement in the middle of the top run at the tightest point. Another possibility is that the gearbox moved after you set the tension. What happens is the final drive chain will pull the gearbox back under load which over tensions the primary unless the adjuster is locked off with firm pressure against the gearbox to prevent it doing so. This may have occurred a few times if you were unaware and you made a number of readjustments during 'bedding in'?
Maybe then a combination of lowish oil level, chain a bit too tight after initial set up and running on a clutch basket that was possibly more worn out than you thought it was when you fitted the new chain has hastened its end. In addition if there is severe runout on either the crank sprocket and/or the clutch basket then the chain will suffer. You mentioned setting the tension at the tightest point which is correct but how much did the tension vary between tight and slack?
All you can do really is check everything is running within limits, replace all the worn out parts and this may now include your new crankshaft sprocket too unfortunately and start again.
