You're not getting ISO 100 because of High Light Priority is turned on. HLP can be useful in an extreme circumstance but it's better to turn it off most of the time unless you want extra noise. Also, turn off ALO, it only screws up exposure setting. And, use Neutral or Neutral based custom picture styles with noise reduction setting set at low. If you use Standard or Standard based picture styles(All the Canon Picture Styles are Standard based except Neutral), it smears detail for noise reduction. If your noise reduction setting is at Standard or above, it'll also smear detail for noise reduction. The kicker is that it smears detail regardless of ISO settings meaning that it'll kill detail even when ISO is at 100 (Low setting only targets color noise so it keeps detail.)
Now you understand why Canon's camera get bad reviews in terms of detail/resolution and why people complain Canon DSLRs are not sharp compared to others.
One more thing: use Magic Lantern if you want to use in between ISO stops such as 160. 2/3 ISO stops are good if you want the least noise when shooting video (less to more noise ISO stops: 160, 320, 640, 100, 200, 400, 800, 1250, 125, 250, 500, 1000, 1600, 2500, 2000, 3200, 4000, 5000, 6400.
However, keep it mind you're making trade off here. While 2/3 stops offer less noise, it slightly reduces highlight dynamic range. If highlight clipping is bound to occur, don't use 2/3 stops.