Live $1650, 250/500+50, far from money, 9-handed

UTG+2 (t30k) opens 1300, BTN (t12k) flats, I'm in BB (t24k) with T9o

Opener is tighter than avg. BTN is looser than avg and kinda bad. Price is 3800 to 800 =>  17.4%

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    equity     win     tie           pots won     pots tied   
Hand 0:     43.486%      42.01%     01.47%       173127755028     6070227642.00   { 66+, A7s+, KTs+, QTs+, JTs, ATo+, KJo+ }
Hand 1:     32.508%      30.84%     01.67%       127084612044     6874750140.00   { AA, 99-44, AJs-A5s, K9s+, Q9s+, J9s+, T8s+, 98s, 87s, AQo-ATo, KJo+, QJo }
Hand 2:     24.006%      23.39%     00.62%        96379396272     2546622810.00   { T9o }

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What do you expect R to be in this spot?

And what's the largest open size you'd flat?