What currency are we going to use, and what's the solution if not a currency union with the UK? If we do have a currency union with the UK, how do we address the fact that we will be using a currency where rates etc are set by the government of a foreign nation?
I think it most likely that we will establish our own currency, possibly pinned to the Euro. I'm no expert, but staying with the pound sterling as it plummets in freefall doesn't seem like a good start to me. Of course this will accelerate the decline of the £, so we'll have to do something to mitigate that. No idea what. :( But hey ho, they told us last time round they wouldn't "let" us use the £, so they can hardly complain if we don't now.
(Of course, we could have continued to use the £, they couldn't stop us. But it does put an important economic lever in WM's hands and we're better off without it. We could also choose to use the € though we could not join it.)
Will we be allowed to rejoin the EU? If so, how do we avoid a hard border with England if they haven't entered into a customs union with the EU?
Very probably, and without any major issues. Our legislation is all currently EU compliant, we would be net contributors, and we're getting friendly noises atm. Spain has specifically said they have no interest in vetoing us, and there is no "queue", so with goodwill on both sides negotiations should be amicable and swift.
Sadly this would mean a hard border with England, I can't see any way round that. But this border is much shorter than the border in N Ireland, far more easily policed with fewer roads, and doesn't come with a hundred years of violent history. So yes, you'll need a passport to visit your English cousins, which will be a pain, sorry.
How do we diversify our economy?
What do you feel we are over reliant on? Our economy is already pretty diverse, and we have new tech companies setting up.
How do we protect ourselves if a Cold War between the US and Russia breaks out, or Iran develops a nuclear bomb?
Stay out of it?
If there's another referendum I'll approach it with the intention of making up my mind anew - I am very open to being persuaded by the independence movement, but it will have to be on the basis of solid factual evidence.
Sadly it's difficult to provide "solid factual evidence" about any of these things, fairly informed conjecture is the best any of us can hope for.