I think lentils would be the best option (if you can digest them). They have next to no sugar and much less starch (and much more protein) than beans. Ultimately, it depends on what you can tolerate and what allows you to progress, but avoiding starch never hurts. Tahini might be another thing to add if you can tolerate sesame.
I’ve also wondered if amino acid supplements like glutamine and carnitine (which help heal the gut) count towards protein intake. Anyone know how these add up?