So, your 8 rep squat is ~55kgs, but you can do 45kgs for 20 reps? Seems a bit off...possibly you're losing depth in the 20 rep near the end, or you should try to put more weight on for the 8 rep set.
When i am doing squats, i try do a completed reps of between 6-8 reps. After i do 75% rm and do adarq's 20 repper squat.
So i can possibly do more but i want to do the reps between 6-8 reps and progress to next weight and aim for those reps and i can advantage of my body i deloading 5kg off and do that for the 20 repper squats.
So yeah, i try complete 6-8 reps of squats and if i can hit those i increase the weight by 5kg and do 6-8 of those and keep progressing from there and my 20 reps, the depth is the same but i feel both of my squats are not good enough depth as when the weight gets heavier my body cheats to get to avoid getting to a point where i feel i won't be able to get up.
Well, the 20 repper should be hard as fuck (the last time I did it, with a max squat of maybe around 155kgs at the time, I did 100kgs for 20 reps and it was brutal, barely finished). There's no way I could do 20 reps by just dropping off 5 kilos from my 8-rep max (prob 120kgs).
If you're having problems telling if you're hitting below parallel, a cue I use is that when you feel your calves and hamstrings making contact, then you are probably past parallel depth. My advice is that you have a session where you just try and get as deep as possible with low weight so you know what hitting ATG depth feels like. Then you'll have a better idea when you start your work sets. Also, improve your squat flexibility by doing deep squat sit holds and stretch your adductors and hip flexors before you go too crazy. One mistake I made was not being flexible enough in the RoM of the full squat before doing it at high-frequency.