I was desperate too with what I perceived to be the same problem your having. That's why I purchased the split ender. Though it's not perfect, my hair feels a lot better. I think those different length splits were helped. From here on I'm not going to go so long between trims and I'm going to be careful about using too much protein as well.
What I do now with my hair to protect it is that I use Giovanni's direct leave-in and an oil that I know from the ingredients that it doesn't have any "cones" in it. I recently found Katawentz Braid Oil at an Oriental BSS. The ingredients are: Jojoba oil, Olive oil, Sesame oil and Castor oil. Then as needed I use Bumble and Bumble Leave-in (rinse out) as my conditioning moisturizer and again I use a little of the oil above or some of Fantastix hair thickener with pure wheat germ oil and honey. I don't mind the oiliness because I put my hair in a bun and then apply a baggie when I'm around the house, if I go out I put on a phonytail. I started this routine this past week. So far so good. But I must warn you if you purchase the Bumble and Bumble it is expensive but presently to me it is worth every penny. My hair feels great!
Let me know if you need any tips on the split ender when you get it. Here's one: Use it in a systematic way so not to repeat over the same area twice, do areas no thicker than 1 inch and no wider than the Split ender tool, on untangled hair.
Edited to add: My hair is relaxed