Awwwweeee! He's so handsome!!!! I could just love him up
Since he's not sleeping with you and his fur's so short you may want to invest in a few doggy pillows to give him a soft and warm spot to lay but be close to you! He's trusting you already if he's sleeping close to you like that! Great Job with him!!!
Also you mentioned he cowers when you reach for him, are you moving slowly and placing your hand palm side up so he can see there is nothing in your hand and he can smell is? This is the best way to approach a scarred dog and have your hand low, try not to stand over him, lower yourself down so you're less threatening to him. If you were to get down to his level and look up you will see how huge everything in his world looks and if he's been abused that's a very scary place. Doing things like offering him a little kibble in the middle of you hand and talking slow and sweet to him will help tons.
I hope it all goes well when he meets his siblings on Monday. Please, keep us posted and know we are here for you if we can help in anyway. ((((Hugs)))) for the rescue of Willie, or Nelson, or Harley. PS: I vote for Harley (have one
) and he looks like he needs a strong and confident sounding name.