Maximizing our value with the nuts - sizing?

Blinds: \$0.10/\$0.25 (9 Players) MP: \$9.90
UTG+1: \$35.01
MP+1: \$14.75
MP+2: \$25.00 (Hero)
CO: \$25.21
BN: \$49.63
SB: \$29.84
BB: \$31.54
UTG: \$38.31
57/29 (7)
looks like a big fish:)
Preflop (\$0.35) Hero is MP+2 with K K
2 folds, UTG+1 calls \$0.25, MP+1 folds, Hero raises to \$1.10, CO folds, BN calls \$1.10, 2 folds, UTG+1 calls \$0.85
Flop (\$3.65) A 9 Q
UTG+1 checks, Hero checks, BN bets \$3.49, UTG+1 folds, Hero calls \$3.49
Turn (\$10.63) A 9 Q T
Hero checks, BN checks
can we consider donking here exploitatively? 1/4-1/3 sizing if so? Maybe a little bit bigger given his flop sizing - his range is supposed to be polarized to TP+
River (\$10.63) A 9 Q T 5
Hero bets
Given his line potbet flop, check turn - I see mainly hands without a spade in his range.. maybe some AxJs at best and lower flushes.
However, how would you choose the optimal bet sizing in order to maximize our value? I would expect that his calling range is gonna be inelastic (except of few XxXs combos)

I see it from a few different angles:

1. We wanna look bluffy and bomb it - he might think that we wanna steal the pot from a split. 100%+
2. Bet so tiny 20-33% that he might think that he is good often enough and the pot is already pretty big
3. Bet somewhere in between 40-60% to still offer a decent prize for calling with the flush

Would you choose any of these 3 options and why?

Or did I miss something?

Cheers