I feel your pain....we have a picky eater too. He's 4 now. He has some sensory issues....textures, smells, etc. Plus we had him evaluated at the children's hospital and found out he had a chewing issue.....thus he tended to just want soft foods.
The first meat he would start to accept was a McDonalds hamburger (plain). For a long time he would just eat the bun, then we had him start dipping the burger & bun in ketchup. The children's hospital explained that McD's hamburgers are the first meat they recommend for problem chewers since the meat is processed and easily chewed.
The second meat he would eat was Chick Filet nuggets, cut up in bits. And now finally he accepts other types of nuggets as well.
We used to push dairy a bunch....milk, yogurt, cheese. He had a tendency to throw up almost daily. We thought for a long time that it was the texture issue and a gag response due to the sensory troubles....but it turned out to be a sensitivity to dairy. We now limit his milk to just a little per day, and only 1 yogurt or cheese slice per day. His ped said this is fine. We also give him vitamins.
One thing I did learn....gummy vitamins do not have iron in them. So we now give him 2 gummys one day, and the next day we give him a Flintstones Complete (with iron).
Have you tried those Gerber chicken sticks....they are sort of like vienna sausages.
Another thing the hospital had us doing was for the pickiness...we were to be on a strict eating schedule, with no milk in between meals & snacks.
As in:
breakfast
midmorning snack
lunch
afternoon snack
supper
bedtime snack
Each meal and snack we were to serve one preferred food, and two non-preferred foods. Only a teaspoon full of the non-preferred food. I was supposed to make sure it was a carb, veg or fruit, and a protein. It was hard to keep this up....I did finally get him to accept fish sticks (baked in the oven). Also I got him to accept another food that way, but I forget now what it was. Also we were told to never prompt him to eat, don't nag, just present the plate, and it was his decision what to eat.
There's a pretty good book called "Just Take A Bite". You might see if your library has it. I found a lot of good info in that.
Also for the chewing problem....the only way for our kid to overcome that was to practice chewing so I went out and bought a few stick foods for snacks....the oreo dippers, graham cracker sticks, etc. Would encourage him to take bites with his big boy teeth, (side teeth instead of front ones).
Well, that's probably more info than you wanted. Hope some of it helps.