That was great that you took them in and are willing to take the rest of the herd in. Since you already have B Complex, you could give him B Complex daily for a few days. Unfortunately, you just need time and patience.
Good luck with them and I hope they all do well for you.
Also I hope that person gets the book thrown at them for such horrible neglect.
I can't remember from the other thread what kind of milk you have been feeding spider, or if this was suggested, but their is a high calorie milk mix that might help.
You take a gallon of whole milk
poor out 3 cups
add 1 can evaporated milk(not the sweetened condensed)
1 cup buttermilk(highest calories, highest fat if possible)
and 1 cup honey.
Since this is very high calorie, and he isn't eating a full feeding, it may help.
You wouldn't have to do all of this or exactly this way. You could just mix one bottle to try it, and see if he would drink it. I would start out slow, just add a spoonful of eveaported milk, see what he does, then try adding a little honey to the bottle.
Don't know what your weather is like, but fresh air and running around on the grass is always good for them, so if you haven't taken them outside to play, I would recommend it.
When I had read your last post, I was thinking to myself, where did these kids come from that their mom died and they hadn't eaten in 24 hours? Your story is very sad, but I am not completely surprised to read it, but worse than I had thought.