nice back! boston's love their frisbee. you should look into getting a Kong .they'll probably fly a little better than the one you're using. it might be harder to catch at first but your boston will get used to it.
Sweet. He weighs about 19lbs. Not too small, not too big. He's a leaner Boston like his dad was (but Jax is more muscular because of frisbee and hiking). Check out the moms and dads of the pups you look at. It's your only indication how big your pup 'might' be fully grown. Awesome dogs, just read up on them and make sure they fit into your lifestyle, i.e. if you're a runner and want a dog to take on long runs, don't get a Boston. If you live in a very hot climate and want a summer hiking buddy, probably not for you (although they have cooling vests that help with this). They don't tolerate the heat (or cold) very well at all. They are athletic but do have their limitations. They are fun as hell though! Any other questions let me know!
Does he catch it though? I think the key might be to start out with really short tosses. He needs to be able to catch it first before you worry about jumps. Does your dog like to jump at all? It sounds to me that your dog is just smart lol. He knows it's coming down eventually, its best to wait it out. =)
Hey Vau. It's made by Kong. Look up "Kong Flyer" on Amazon. If you're looking for a soft plastic which will fly a lot better, check out Hero's line of discs for dogs.