I rescued a 4-5 year old male from an owner who treated him more like a cat. Never spent quality time with him, never trained him, no routine, ignored him, yelled at him, and never took him for walks (didn't even own a collar when I got him). Little Benji didn't even own his own bed!
I noticed he was very curious at first about our family, our house. You have to let him explore, get into trouble and use posititive reinforcement only. Especially if you suspect your dog was abused, using negative reinforcement will only cause more damage. Fore example, Benji was obviously use to jumping up on counters to see what's going on, or on the dinner table. In 2 days he was trained to stop doing that with a simple squirt bottle. Now he only needs to see the squirt bottle and he knows it means not to jump. Some habits can be changed, others could be a little harder but use treats and lures to start changing habits. Eventually the lures won't be needed and he will do it because you tell him he is a "good boy" and loves to hear that from the whole family.
My Benji was also very jumpy when you approached him at first, didn't even know how to walk on a leash… but I started walking him 3 times a day and that is the best way to get him use to being very close and beside you. Get all family members to do this and spend one-on-one time with your Prince. Now, Benji just LOVES going for walks. I also went through a lot of treats the first 2 weeks, teaching him to stop on command, sitting at streets, and of course my favourite saying "Let's Go" and watch him run off like a mad man!
Benji now has two beds, stays off the couch, off tables, comes 50% of the time you call him (that's just Basenji trait - hehe), and loves the whole family. I'm now only in the 3rd week and can't believe the transformation of little Benji. He's sometimes up to no good, like chewing apart a bunji cord to keep a gate in place, or clawing a door frame to try and escape confinement, but hey he's a dog not a robot....