If that pup doesn't have German shepherd in it then I'm a monkeys uncle.
Our Wally came from a silimar situation, minus the dementia, tied up all day and hit around the head when he barked or misbehaved. Had never been to the beach.
The first few weeks as a soon as the gate opened he would make a bolt for freedom. Now even with an open gate he is happy to stay in the yard.
What a lucky dog to have found such a wonderful home. I'm sure you don't need advice but ...
And well done... every dog deserves a great home.