Why wouldn't you muzzle him to stop the damage initially until he gets used to being alone extending the time a little more each time - I know it doesn't stop the clawing damage but he should be shown and chastised for that, so he knows it's not acceptable. We took a doberman from the rescue society years ago to be a guard dog on our farm that was going to be put down because they couldn't rehouse it due to aggression. My hubby could do anything with that dog, but I recognized to be careful around him and when feeding him, he knew male authority and was hard to break to female authority being me. He served his purpose well till he had a heartache with being overly hyper. My hubby is hyper strict with a new animal of any description and gives them the attention they need at the front end to instill good manners and hopefully retrain any bad traits. Patience, love and a firm hand/voice has always worked for us.
Appreciate this is a puppy and it will be 9 weeks old in a couple more days, which hopefully comes with less history baggage and mental damage than with a rescue but ............
Daughter and fiance just got a GSD puppy at 7 weeks, first week odd pee and accidents, in-between taking her out every hour when she was awake or immediately after eating/drinking (not one poop in the house yet and only 2 on the deck) but I at home with her during the day, scolded and made her know not acceptable and I take her out lots to do her business in our front paddock. We have just completed Night 3 with zero accidents day or overnight, and she asked to go out for her poop this morning by crying at the door. When she wants to pee she comes and sits looking up at me so far and I scoop her up and take her out to the field. If she follows me out through the garage she'll typically pee on the tarmac drive not getting to the field. We disinfect clean every time she's done anything to get rid of any smell immediately to avoid association that it's acceptable.
I'm sure she might have an odd mistake moving forwards but she has been day time clean for 5 days with zero accidents and night time clean for 3 nights. We are very routine and make sure she is exhausted through play before bed at around 10pm and then out at 5.15am when fiance leaves, and out again at 7.15am when I get up.
First four nights she cried (got less each night) due to anxiety being locked on her bed in the utility room - she got soothing the first night, but after that I told them to ignore her or they'd make a rod for their own backs. We don't allow pets on our furniture or carpeted areas but spend time playing with them, and they come out doing chores with us. We are very strict when they are puppies so they don't become obnoxious or a PITA adult dog. My beautiful retriever that passed two years ago this Sept I miss like crazy = she always greeted me coming home, would turn away when we sat down at the table to eat, never went on our carpets or up/down stairs. We would leave chicken on the lower counter in the kitchen, chocolates and snacks on the coffee table in the front room and she'd never touch anything. If it was on the hard floors in kitchen, hall, utility area floors it was hers and fair game. If you told her not to touch a treat she'd drool and not until you told her "go on". Any dog can be trained over time with consistency, learning to read their signals and most importantly being strict at the front end - they are pack animals and need to know they are not going to become the Alpha dominant in the household.
We even have a horse he's now 16, that when we got him at 4 was head shy and we found out he'd been nastily broken by a cowboy with a metal rod after the fact. It took a long time it felt to gain his trust, for him to know "this is my space, this is your space" when working around him and so on. He is the most dynamite family member we could wish for.
I truly believe any animal with patience, kindness and strictness regarding respect and what's expected of them, and reading their signals we can train to become a pleasure to have around. Some unfortunately are so mentally scarred we have they require a lot more attention and patience or some leeway in certain respects until ....... However, the proviso is, we shouldn't take on the task unless we commit to the time and attention needed to do so.