Iacchus said:
Of course once you're dead and gone there won't be anything to prove to anybody now will there? Unless of course you're wrong ... 
A little more of Pascal's Wager floating in there? Chances are of course very good that you're wrong, too. Vanishingly tiny chances that your tapestry of unsupportable assumptions is anywhere near right. You're at a (charitable) 50/50 for a god, a 1 in 4 for a god and a meaning, 1 in 8 for a god with a meaning, who cares what people think. Start adding in all your other assumptions and we're probably a lot more likely to see pigs fly. Of course, pigs have already flown as air freight, so pig aviation is a known quantity, while your scenarios based on wild ass guesses is just so much fiction.
Or, maybe we should just pretend like we were never here? Indeed, if per chance the Universe began completely by accident, to which there was no rhyme or reason, then it can only suggest one thing, that there is no ultimate meaning in life and, that we were never meant to be. In which case I would ask, What's the point in having this discussion?
It could be the 'ultimate meaning' would be to find a way for humanity/life to survive the life cycle of the universe, rather than wallow in fantasies about (not established as real) doomsdays and a (not established as real) superman who'll show up and rescue everybody and take them all to a (not established as real) happy place for (not established as real) reasons.
Also, can you tell me what existing principles may have existed prior to the Big Bang?
I wasn't there. Right now, we don't know, and I'm fine with that. Perhaps some day people will know.
Assuming the 'Big Bang' was not excessively complicated, (i.e. gods and angels farting things into existence while battling demons and unicorns and leprechains over their lucky charms), then some educated guesses can be made by reverse-engineering matter, light, gravity, whatever other forces and phenomena we discover in the universe, assuming that they're 'real' and predictable (i.e. things in motion don't make 90 degree turns for no reason. )
If all of the matter did come from a singularity of some sort, we might determine some things about it by studying other singularities.