I think by marrow bones you mean the clean, smallish white bones that are just full of soft marrow? These are ok to feed, as long as your dog is not going overboard and you supervise, chipping a tooth shouldn't be a problem. Definitely do not allow him to lick out all of that marrow, it'll upset his tummy VERY much to go from zero marrow to that much all at once. I recommend, for small breeds like himself, a chicken or turkey leg for a good meaty meal and chewing because they can fully digest the bone and it does not pose a danger to teeth.
Oh wait, I just noticed it's soup bones you're talking about!
Soup bones are very big for a pup his size! As long as they have some meat on them, it should be fine for a short session of recreational chewing. DON'T cook it, at all! You can dip it in hot water for a few seconds, if it makes you feel better, but I just thaw raw bones in the fridge and give them to my dogs as is. Watch him and be sure he isn't chewing too vigorously, if he is the bone should be taken away. It can be re-fridged or frozen and given at another time as long as you keep an eye on his chewing.