If Voldemort had the Elder Wand with him in the Battle over Little Whinging, would the Elder Wand have been destroyed? Since he wasn't the master of the Elder Wand then, and in reality, never was, would Harry's Phoenix Wand have sensed Voldemort's power and regurgitated some of it against Voldemort. This coupled with the Elder Wand, not having Voldemort as its true master, only acting like as regular normal Wand, would that have meant the Elder Wand wouldn't have obeyed Voldemort and/or Harry thus leading to the destruction of the Elder Wand?
"...only acting like as regular normal Wand..."
One thing you have to remember about the Elder Wand is that it IS a regular, normal wand. Yes, it's origin and materials make it powerful in the hands of its true master (whoever that may be at the time) but it is still just a wand.
If the wand is not in the hands of its master, it'll still work, which we see throughout Deathly Hallows as Voldemort is able to use it, it just won't perform any more extraordinarily than any other wand.
That being the case, as Voldemort was using a "borrowed" wand during the Battle over Little Whinging anyway, we can expect the outcome would have been to same had he been using the Elder Wand
No. I don't think so. Because even though Voldemort was not the master of the Elder Wand neither was Harry. So, why should it backfire? But the Elder Wand only works for it's master who is Draco. In conclusion, Voldemort probably couldn't even use it.