Sorry for the long title! I am at a loss on how to stop this, or if I should.
Angel acts like he is never fed!

Makes me feel bad! I give him 1/8 cup of THK Embark in the morning mixed with water, evening he gets 1/8 cup Wellness Core (grain free) chicken. Throughout the day, he will get a few treats, some carrots, a few apple slices. He is two years old and weighs between 9 and 9.5lbs. The vet said he should weigh about 8.5 lbs - that was his last physical, he is due for one in the spring. Anyway, he shakes, visibly, when there is any kind of food around. And sometimes he will bark for food!!! I don't want to under feed him, but I don't want him to get obese! he absolutely cannot gain more weight! I can feel his ribs with a little pressure, but it won't take much for him to "pork up!"
I don't know what to do! My DIL and friend were finally able to see how he shakes! I have never seen one shake like him before!
I sure could use some advice! Thanks!