It's hard to tell your dog's age... 6 mo, or 1year and 6mo? If it's the former, then you do not want your dog to jump as his joints are still developing.
But to teach him to catch discs better, there are a few things to consider. If the disc is always falling too far, then do shorter tosses so that your dog can 'win' and work up to longer tosses as your dog develops the habit of catching it before it falls. There's nothing wrong with a dog playing fetch with the disc when it hits the ground, but if that's how the dog plays then that's what the dog thinks discs are for. You can also try using lighter discs like the Chuckit Paraflight because it glides a little slower and tends to hover rather than fall fast. Those light, hovering discs can give your dog the time to catch up. However, the tradeoff is hovering discs hover so your dog may have to jump up to get it. Even for mature dogs, that upright jumping motion is not great for their joints. So the big takeaway is, you should throw your disc in a way that your dog is catching it efficiently and safely, and build up over time.
But to teach him to catch discs better, there are a few things to consider. If the disc is always falling too far, then do shorter tosses so that your dog can 'win' and work up to longer tosses as your dog develops the habit of catching it before it falls. There's nothing wrong with a dog playing fetch with the disc when it hits the ground, but if that's how the dog plays then that's what the dog thinks discs are for. You can also try using lighter discs like the Chuckit Paraflight because it glides a little slower and tends to hover rather than fall fast. Those light, hovering discs can give your dog the time to catch up. However, the tradeoff is hovering discs hover so your dog may have to jump up to get it. Even for mature dogs, that upright jumping motion is not great for their joints. So the big takeaway is, you should throw your disc in a way that your dog is catching it efficiently and safely, and build up over time.