donnae
you are right, even though vets have to study cat and dog breeds, most of them do so from a theoretical perspective, and they may never see an individual of the breeds they study.As regards to your question about pattern, yes your cat is a tabby, just like all bengals are tabby. They just happen to have their very own kind of tabby, being It rosetted, spotted, marbled or a mixture of them.
Ideally, bengals' patterns should be:
-random
-asymmetric
-showing horizontal flow
-clearly defined
-showing great contrast
Note that I said "ideally". I have seen purebreeds from good breeders that lack one or more of these characteristics. They are pet quality, but not less bengal for that.
As regards to ticked hair, It is not a desirable trait, but it occurs even among purebreeds (southern ALC do not have this trait, but the others do, and siempre of the domestic cat breeds used un foundation bengals have this trait too, so is something not that easy to get rid of). Is his ticking very obvious in person? In the pictures he seems to have mostly a well defined pattern. The softness of fur you describe, on the other hand, is one of the distinctive traits of bengal breed.
Finally, I would say Jack is a cool toned brown marbled tabby, rather than a tarnished silver, but this is something difficult to judge without the cat in front of me.
Of course, all my observations about you cat are just my opinion, so don't take them as anything else than that
don't they?--I just can't help but fall in love with him every day. You are soooo right, it doesn't matter his 'heritage' I adore my little furball so much. 
