Wow man, that is rough.
If for some reason the insurance does not deem it as a total loss, I would fight to get them to total the car - you do not want this car repaired.
Related to insurance payout, they operate under some formula to calculate how much they should pay you and often times the first offer will be crap. Don't accept it and don't feel pressured to - its a game where they try to pay as little as possible and you try to get as much as possible. Since it was the Explorer's driver at fault, assuming his insurance isn't crap, they will also probably pay for a rental car so use that to your advantage in negotiating a payout since the longer it takes, the more money they lose on that.
I would pull together everything that you've paid for the car and get the price of every comparable car to yours in your area. The more expensive the better. Essentially, you want to be able to justify asking for a higher price then they offer by showing them what the cost to make you whole is. Don't be afraid to push back and be stubborn but fair. Also, they have to include the taxes in the payout in most states, so for instance if the value of your car is 30K, they would have to give you 33K since that includes taxes (assuming you live in a 10% tax zip code). Don't negotiate with that added in, negotiate without it.
As for gap insurance, I've never had it but have heard that its kinda useless. Not sure what the order of the payouts would be in this case.
All in all, good luck and that sucks.