Whatdidyousay, can you define more what you mean about Marty being "a fussy eater?" How big is he?
Is he throwing up what he eats? Or just not eating much? Or not eating what you give him?
When we got Pippin from the rescue, he had been neglected and possibly abused. His weight was down to 8 lbs. when they got him; it was back up to nearly 10 lbs. when we got him. (He is about 12" tall at the shoulder, so he should have been around 12 lbs.)
By coincidence, my vet offered a "Dog nutrition" seminar shortly after we got him. I learned about the appropriate amounts to feed him, and I was startled at how little it was - about 1/4 c. of kibble mixed with a tablespoon of canned food, twice a day.
Pippin was the smallest dog I'd ever had, and I wasn't used to feeding such small amounts.
Guess what - he GAINED weight on those amounts, and then actually became a little overweight! He is a bit chunky now, at about 14 lbs., but has been stable at that weight for quite some time.
The vet is now telling me that we should give him only about a full *teaspoon* of the canned food in addition to the kibble, to bring his weight down gradually to the appropriate 12 lbs.
So my point is - if Marty is a small dog (which he is, right?) then what seems like a very small amount of food might be just fine for him.
If he really is not eating anything at all, then I would try small amounts of boiled chicken (or microwaved - I put chicken in a Corningware dish with a bit of water and cook it for a few minutes in the microwave when I'm making it for the dogs). Let cook, chop it up, then add a little bit of rice to it.
If he will eat that, then you can try chopping up carrots, green beans, or a bit of apple, and combine it with the chicken and rice.
Did the venison work for him? As I mentioned before, neither of my dogs liked venison at all. Casey threw it up and Pippin wouldn't even eat it. I don't know if that's a poodle thing or just particular to them, but venison definitely was not a success.