It seems like M+20 is 170, and M+21 is 177, and M+18 is 156. This is the base score (before the 1.5x best week multiplier). Your base score for that 11, as you stated, is 98. Since you timed it with three minutes to spare, I think the base score for 11s will be 97 or maybe 96.
All 20s is still 2720, it may have changed at the intermediate levels with the change in affix distribution. Now, there are two affixes at 7-13 and three affixes at 14+, there is a little score jump to reward people for adding another affix and the score jumps seem to have moved.
I think it has changed earlier. A +++6 from season 1 has a base score of 70, but a +++6 from this season has a base score of 65.