Free trade doesn't require membership of the political union.
'More jobs' requires a fair amount more explanation. I'm not aware of any research that links our membership of the political structures of the EU with more jobs, beyond those dependent on the bureaucracy of course.
'Low prices' - on what? Certainly not on products purchased from outside the customs union, those are more expensive due to the tariffs we're obliged to apply in order to protect uncompetitive European producers.
Freedom of movement is indeed an advantage although of course people can and do work in other countries without being in political union with them.
Obviously we would lose our say in European issues, however they wouldn't for the most part be our issues anymore as we wouldn't have to abide by these European decisions.
Workers' rights gets down to another issue. We're a democracy and if we want those and other rights it's simple, we vote for those who will provide them. If others already voted for try and take them away we ensure that they understand this would be a bad idea for their re-election prospects.
If we regard it as a good thing that the EU can overrule our Parliament on the grounds that you or others may like what they have to say some of the time we may as well not bother with democracy at all. Democracy rarely pleases everyone all the time.
As far as unproven risks go what is very clear is that the EU is warming up to hit us with a series of unpopular measures as soon as the referendum is done. That's no unproven risk; the budget is going up, we're going to be paying more of it, unpopular measures are being held back until after our vote. Even things like the rather laughable concessions Cameron won or the 'tampon tax' change can easily be prevented. Especially the 'tampon tax' change, which it seems is a non-starter beyond scoring political points for Cameron and in turn the remain campaign.
So with those in mind still waiting for that positive case. I'm yet to hear anything that suggests political union is a good idea.
If I may ask you something - where are all the other 'Unions' in the world? How come the 500-ish million of us are the only ones who've enacted a political union? Do we know something the rest of the world doesn't? Looking at how the European and especially Eurozone economy is performing compared to the rest of the world I can't say the economics of our decision are clear.
Watching things like
this I can't say it seems to be good for international relations either.
EDIT: On your point on the stock market it's a bubble-icious QE-pumped mess, blown up by corporations borrowing to buy back their own shares and large quantities of corporate and private debt. Pensions and investments are already delivering poor returns due to ZIRP. Out of every period of uncertainty come winners and losers and something of an economic reset may actually be beneficial beyond the immediate term.