Huh, I wrote a post and it didn't send. Interesting.
Anyway! First off, give him time! While it's possible that if you know he was beat he may have had all drive to play and interact with "stuff" beat out of him, it's also possible that he doesn't understand what you want him to do yet because he doesn't know who you are yet. It's only been a couple days, he's allowed to be confused.
I personally wholeheartedly recommend doing at least an edited version of the two week shutdown. I did one with Skoll and it made a HUGE difference. Now that said I've only had my boy for two months and he still opens up a little more each day... last night was the first night that he was content to lay sprawled out upside down, and recently he's taken to cuddling up to me at night instead of sleeping in his crate (with door open). Slow steady steps.
Remember if your boy has never been walked before there is suddenly a HUGE world outside of his previous place and he just has so much to see and do and sniff and pee on
No wonder he pulls! Keep walks short and sweet, start in your backyard or even in your house and perhaps just take him around the block a few days and slowly expand from there. If you lived in a closet all your life and suddenly you learned that there was this great big world outside you'd be excited to experience everything too. At least now he can live like a real dog
If you need a training aide try to keep a head halti as a last resort (there are some who feel with dobes at risk for wobblers a halti is not so good)- I use one on my boy when he gets too antsy about dogs but I have him on a short leash so that he can't dash and whip his head around.
Also, try running him around or using a flirt pole. Most dogs with any amount of prey drive can't resist!