You are backwashing correctly. After just a backwash, only add 80% of the clean charge. It never washes off completely. After a teardown and cleaning you use 100% of the DE again. See
DE Filter Cleaning Tutorial
The unfortunate part is that unless you run all the pool water through the filter and empty it into another pool, you won't get 100% filtration. What goes through the filter gets filtered, but then it gets mixed with dirty water and run through again and again and again.
For simple math let's say it takes 5 hours to filter your whole pool. So in half an hour that's 10%. Or 1% every three minutes. After the first three minutes, you'll have 99% of the crud left. An in another 3, 99% of 99% and so on and so on with diminishing returns every 3 minute block. There's 20 3 minute blocks in an hour. So .99
20 is .8179, call it 82% of the floating debris is left in the pool. That's pretty close to 80%, which is what you'd expect after 1/5 of the turnover time. But then it falls off as the already-filtered water portion gets larger and dilutes the dirty water. 5 hour turnover means 100 3 minute blocks of time. .99
100 leaves 36.6% of the debris still in the water. After ten hours of filtering -- that's 200 3 minute blocks -- you'll still have 13.5% of the debris in the water.
So, no, it won't get clear in 5 hours just by filtering. Also note that if the chemistry isn't right, you may have algae growing in the pool while you're filtering it out and you'll end up in a stalemate with nothing to show for all that filtering and backwashing. "Chemistry is close" needs to be "Chlorine is at shock level for our CYA" if you want a clear pool.
