Sansevieria woes - am starting to yell at them - help please!

Hello all!

I have read every word (yes, every!) written on this site and the Internet about Sansevieria plants and their issues, though I was sure I knew how to take care of them before that. I remain utterly stumped so I have finally decided to be brave and post and ask for your wisdom.

I have a Giant Sansevieria plant that has been in my life since I was born - it being given to my mom in a small pot the day I was born (50+ years ago). She gave me part of it about 10 years ago as a housewarming gift and I've had to divide it three times - some of the plants are taller than I am. It's dark green with no other color.  It has always grown like a weed and finally cracked the pot it was in, so I divided it about 3 years ago, again, into 3 pots.   

It never really grew after this. None of it. It sent up a few new leaves but nothing to get excited about. Over the years it has been dying. I have given it the same careful care.  Some of the leaves were drooping over like a tree falling in the woods (I'd carefully repot them deeper).   Many were bending over, limp, as if they were getting way too much water, and this would go on and on and on even though I wasn't watering it any less or more. Meanwhile other leaves, even right next to these, would be wrinkled and so, so skinny as if needing water badly.  I just clipped off the badly drooping leaves, made sure there were no bugs or fungus and kept hoping it'd bounce back. It didn't.

I transplanted them all 2 months ago as there was so little left and I'd convinced myself if I made extra sure I had fresh soil, fresh pots and was extra careful, I'd right whatever wrong was there.  I ended up with two smaller pots, I threw SO much away. A few roots were mush while what I found were very, very few new growths or  basal rosettes.  Many of the leaves were shriveled at the base and so thin they were like pencils. It's like the plant had just stopped where I'd put it last time.

I put it in smaller pots with 1 part soil, 1 part peat and 2 parts of small fish tank gravel (not dyed). Good drainage holes. They're on my porch, indirect SW light.

They're doing the same thing all over again. The outside leaves are dropping and bending at the middle all the way to the floor and the bases are getting so skinny and shriveled. The tops are still wide and healthy looking. I see one little new leave poking out of the soil.  I'm at a loss and don't want to lose this whole plant.  

I give it dirty looks every time I take the trash out and pass it on the stairs, calling  it ungrateful, and I know that's not the way to go.    I appeal to your expertise.  Thank you in advance!