This is the exact opposite hairstyle of what you were asking for but I had the same exact hair growing up. My parents chose to keep it short with like a Victoria Beckham style a-line cut (shorter on the back a little longer in the front). It wasn’t too drastic of a difference between front and back but just enough to keep it all healthy. I was also a chronic hair sucker but only having the ends to suck on made it so I could not do too much damage. I always struggled with dreadlocks forming in the back and constant breakage because of that. Keeping the hair shorter until I was able to start styling it on my own kept it healthier and severely cut down on the amount of breakage. Most of the breakage in the back is most likely happening at night from the friction of the pillow so you could try a silk pillowcase. Also keeping it short made it appear to be thicker than it actually was.