I can't speak for the entire leave electorate. Ailicece, just myself.
To address your points...
I don't believe immigration will diminish enormously or immediately; but neither am I convinced that uncontrollable free movement is A Good Thing End Of Argument.
I believe that the economy will suffer in the short term... As we are seeing today. But I have faith that it will recover. Do I believe nations will be 'queuing up' to sign trade agreements? Maybe not (do they with any country?) Do I believe we won't be able to trade now we're out of the EU? Absolutely not.
I have no idea what 'sovereignty' is.
The EU is massive, unwieldy and undemocratic in my opinion. It is a layer of expensive bureaucracy which, although has some positives, we simply don't need.
In my opinion.