Welcome to the forum. It's apparent that red flags have gone up and you are right to think long and hard about getting this kitten. I know a breeder from the Ukraine that puts their kittens on the Facebook Page "Bengals the beautiful cat". They usually have kittens that are older. Their prices are quite high, in my opinion. May be a totally different breeder! Legitimate breeders of purebred cats have no problem issuing the necessary papers proving a pedigree. Without the papers, you will never be certain your kitten is 100% bengal. There are DNA tests that can be done that "point" to a breed but even that can't prove 100%.
As for your kitties getting along, if they are introduced properly, things do go better. That means, keeping your new kitten in a "safe" room (this is done for multiple reasons -- to keep the cats apart if there is a transmittable disease and to secure a smaller, safer environment for the new arrival).
Cats are priced differently based on several things. Location can affect this -- the type of cat (show cat, pet quality). There is no set market price for a bengal kitten. It's whatever price you can agree upon.
As for the markings -- bengals are born with what they have. The pelt can change over time, especially as Deputy said -- in snows and silvers.
Since the vet refused to allow you to take a picture, I'd be a little hesitant. However, there is a kitten who needs a loving home. If you do not care whether the kitty has papers or is a purebred bengal, and you want to spend that kind of money .... by all means do. There are other bengal breeders listed here:
http://www.topcatbreeders.com/breed/bengalYou may find for the price you can actually purchase a purebred bengal from a registered breeder. The BEST thing is to always visit a breeder in person! Tour the facility and see the kitties. Outside of that, you are taking a chance and there are scam artists out there everywhere. Shipping a cat to another country isn't always the easiest thing.
Deputy gave you some great pointers, too. Hope others will weigh in.