17k is possible, though I'm surprised that that would constitute a diving pool. But don't round down. PF is 7, so 1 lb of stabilizer will increase your CYA level by 7 ppm and 1 lb of dichlor (55% chlorine) will add about 4 ppm of chlorine (0.55 x 7).

Then, backwash at 15 psi. It's good that it's increasing that quickly; that means the dead algae is not 'leaking' through the filter, which can happen.

Get a cheap OTO (yellow / red drops) test kit locally, and use it for now. Maintain chlorine levels in the dark yellow to orange region. If you reach 'orange' let the chlorine drop to dark yellow before adding more.

Brush. Vacuum.

Once the pool clears a bit, make sure the chlorine is high, and then turn the pump off for 24 hours. Much of the algae *may* settle to the bottom. If the algae settles, make sure the pool returns direct water AWAY from the bottom, turn the pump back on, and began vacuum algae off the bottom. 'Walk' bleach around the pool if the chlorine level starts to drop while the pump is off. If the algae does NOT settle, just turn the pump back on and continue filtering.