Is it only around food that he is anxious? Do you have a normal feeding time routine? Do you walk otis before you feed him?
I have an anxious dog and a dog that was severely anxious but is normal now. What I learned is that it is really important not to make a big deal about anything. Also, they like routines-even if mealtimes are not at the same time every day (say due to different shifts, school, schedule, whatever) there is still a routine. Like walking before a meal ("earning" their food), even if it's just 10 minutes (although more exercise usually means less anxiety). Then, my dogs each have a certain spot they sit in while I am getting meals ready. They don't get food if they are whining, pacing, etc etc. A nice calm sit-stay as I put the meals down, and then they get released to eat.
If your dog doesn't want to eat-you can't force him and I wouldn't try. Just like people, if we don't want to eat, we're not going to! Following the feeding routine, leave the food down for 15-20minutes and if he doesn't eat, pick it up.
What have you been working on with him to build his confidence and decrease anxiety since you adopted him?
Oh and straight from my own vet's mouth-"No coddling!" If he is being anxious, don't pat, soothe, talk to him, or reassure him, as you're then reinforcing that his anxious behaviour is good and deserves reward. That's why at my house whining pacing dogs do not get fed, only dogs in a nice sit stay who are not anxious or excited get food. With the new puppy, sometimes that means a little bit of a wait at meal times, although she is getting better!
I hope others have some more suggestions for you. I think the most important thing I've learned from dealing with my anxious dogs is not to coddle and reinfoce the anxious behaviour, and do not make a big deal about anything or it just makes them think there is something to be anxious about.