Well I don't want to lead you down another path that you may be following from another poster here. I think they all intend to offer solid advice.
Have you done any vacuuming to waste yet? Maybe you don't know what that means at that point so I'll make a quick as possible explanation.
I don't recall you mentioning what style of sand filter you have. Mine has a multi-port valve on top which you move only when the pump is off. There's settings like filter, waste, recirculate, bypass, backwash. See pictures below. Disregard the random junk. In the photo of the sand filter disregard the orange cord and motor sitting next to it, it's just sitting there and has nothing to do with the pool.
Anyway when you have it set to waste it will send everything pumped out the waste port. So you need to have a waste hose that can reach to wherever you want it to go. You can buy that lay flat blue piece of garbage for $20 and have it blow out after four uses or you can buy some sump pump hoses at Lowe's or Home Depot which are much more durable.
I think you need to do a bunch of vacuuming to waste, I feel like you must have a bunch of organic material at the bottom. I don't think your sand filter is going to handle what's there already.
Opinion Alert: Anything the pool store sold you or gave you is working against you. I swore to not use anything but Clorox bleach, muriatic acid, arm and hammer baking soda, and stabilizer from Clorox. Unfortunately I had a moment and decided I would just use up the two bags of shock the pool place gave me. What a mistake, everything went downhill from there. (my store will give me lots of freebies to get me hooked, then they'll start charging)
Maybe you should post a picture of the chlorine / bleach you are using, the acid you used, the baking soda you used, the stabilizer you used.
If it is an option it seems like a major drain and refill would help you get where you want to be much faster, however that's probably about $140. Of water or more and then you'll have to add in everything else again