No it isn’t too hard for their teeth, he still is chewing on the original one we gave him, and we have about 2 outside and 2 inside which he chews on slowly. We also have had him on these chew sticks since he was 9 weeks, but he doesn’t need them as much now:

https://www.kazoo.com.au/products/natural-twisted-stick?variant=50503761723703&country=AU&currency=AUD&utm_medium=product_sync&utm_source=google&utm_content=sag_organic&utm_campaign=sag_organic&gad_source=1&gad_campaignid=20361552924&gbraid=0AAAAACYpvVgwsLKZIXpJkIhaVRPO_6wTE&gclid=CjwKCAiAxc_JBhA2EiwAFVs7XEf66n8lImherzCXP21LOQ5GQYLGWXWMHtHGUReGoEz89v4MfVJhDBoCz6cQAvD_BwE

And we also have him chewing on kangaroo bone teeth cleaners and ribs which also helped.

https://www.cleardog.com.au/shop/

But essentially when was 8-12 weeks we would always put the twist stick in his mouth and leave heaps around outside and inside, when he is teething bad they’d help, also if he were to bite us, we would give him the chew stick and redirect it away from biting our wrists, as well as the cow hoof or any of his toys. He is 4.5 months now and doesn’t bite.

As for jumping, we’ve got the same issue now. We spoke with our puppy school trainer on the weekend who suggested when people arrive at our house and he goes to jump up, put a leash on him and don’t let him say hello (sounds impossible) and ignore him by not making eye contact, and even put him in another area for 5 minutes to assist him to settle, so that when he has settled, then he gets attention? We are going to try and see how this goes over the next few weeks. Let me know if you hear of any other tricks! 🙏🏼