amazing results, congratulations. the fact that you have maintained muscularity while switching to gelatin as your only protein source is great. the loss of strength in the gym is probably more due to eliminating starch more so than anything else, but maintaining or improving muscularity and body comp is a big win, not to mention solving the prior health issues.
i'm not sure what you can do in terms of rounding out your protein intake with complete sources if dairy, meat, and eggs are problematic. peat has spoken favorably of certain foods outside of these 3 varieties having really good quality protein like potatoes but throwing in 2 pounds of potatoes (peat said this is similar to around 1l of milk in terms of protein amount so about 35g) is probably less ideal than your current scheme which seems to be having a small amount of beef for dinner on occasion.
with that said, i think you have the correct idea with how you might use a little bit of beef for dinner, i might recommend experimenting with different cuts to see which ones are more agreeable or less likely to cause issues. i've done remarkably well in the past by using a high quality mince beef while dealing with autoimmune type issues, it's not the worst cut as there is a fair bit of connective tissue in there, but you might be well to experiment with some more gelatinous cuts like lamb shank. you can also make a gelatinous stew using oxtail but i never tried the stuff myself.
