Sorry to hear of your integrating troubles! It can be a hard thing for sure. My most trusted and go to method is the "night integration". I add lot's of things they can climb up on or hide in so they can get away from the flock and also take some treats (I usually use my goat's grain or something small) to throw in the whole run so everyone can get some, idk if it actually helps but I feel like it brings some togetherness to the flock. When it's pitch dark out I take the new comers and place them on the highest perch. It seems to work out most times-either the other birds don't even notice or they see they're on the top perch and don't fight them as much. I don't recommend doing this with roosters however since they will fight way worse than the hens most of the time. It sounds like you're doing great job, I hope this helps 
