Given it's now Thursday, I think I'd follow Musky's suggestion just for now.
There is a series of things you could do, but maybe not in the time available . . .
BSAreg's stuck regulator points is very likely, but it could be a short between F and D at the dynamo, which would also chuck all power out at all times. A constant 8A or more charge rate won't be doing anything any good at all and could (will, probably) cause dynamo failure.
You could quickly measure the voltage across the battery with the engine running above tickover though if you wanted, and if it soars to 'lots' with a few rpm then there's no regulating going on for whatever reason - or it speaks to a very flat battery indeed which, if the charge rate stays so high, says the battery won't accept a charge. If you're at 6v, you don't want to see more than about 7.5v - anything in the teens or above is a recipe for potential extra expense!
Have you blown any bulbs I wonder? Uncontrolled voltage has that tendency, as well as boiling batteries dry.
So I think it's best not to run with the dynamo connected unless you can make the problem go away in the time you've got.
If the battery can support a brake light for a few hours, all well and good, if not - hand signals!
And Yes to a DVR2 - and imho No to a replica mechanical regulator. Better to have the original sorted if you don't want to go electronic, as they are far better-made than any copy I have seen. This is an area where you get what you pay for . . .