Bluffcheckraising river in medium/big pot

I pulled this one out of another thread, how clear is this river call? Why would he bluffcheckraise that river, does he ever get a better hand to fold? My impression of him is that he definitely could be behind on the river (so I agree with Druff's action), but therefore he always get called (yw doughnutz for me plugging your leaks). Does he ever play A5, 66-99 this way?

PokerStars Game #25374932156: Hold'em Limit ($50/$100) - 2009/02/26 9:13:05 PT [2009/02/26 12:13:05 ET]
Table 'Phaedra IV' 6-max Seat #4 is the button
Seat 3: doughnutz ($3750 in chips)
Seat 4: Dan Druff ($2266 in chips)
Seat 5: Pokky Star ($1667 in chips)
Pokky Star: posts small blind $25
importer1: is sitting out
doughnutz: posts big blind $50
*** HOLE CARDS ***
Dealt to Dan Druff [Th Ac]
importer1 leaves the table
Dan Druff: raises $50 to $100
Pokky Star: raises $50 to $150
doughnutz: calls $100
Dan Druff: calls $50
*** FLOP *** [Ts Td 3d]
Pokky Star: bets $50
doughnutz: calls $50
Dan Druff: raises $50 to $100
Pokky Star: calls $50
doughnutz: calls $50
*** TURN *** [Ts Td 3d] [Jc]
Pokky Star: checks
doughnutz: checks
Dan Druff: bets $100
Pokky Star: folds
doughnutz: calls $100
*** RIVER *** [Ts Td 3d Jc] [5d]
doughnutz: checks
Dan Druff: bets $100
doughnutz: raises $100 to $200
Dan Druff: calls $100
*** SHOW DOWN ***
doughnutz: shows [9d Qd] (a flush, Queen high)
Dan Druff: shows [Th Ac] (three of a kind, Tens)
doughnutz collected $1349 from pot

When to flip late in tourneys

$50+$5 daily at Stars, 22 people left. First place is about $15k, the top seven or so places are $2k+ but busting outside the final table only pays a few hundred dollars and would be a huge disappointment after playing for seven hours.

Blinds 5k/10k. I have a little over 200k, which is almost exactly average, the chipleader has about 350k (actually pretty good structure until you get down to final 100 or so ). JJ utg, I make it 23456 or some like that. A guy in MP pushes for 300k. The whole table is pretty weaktight, so he definitely has a hand. Probably 88+, AQ+, possibly even tighter. I considered a Hellmuthian fold, but I really felt there was too much value in calling. The alternative is folding and going the "safe" route by stealing blinds, but a few failed attempts and I would be seriously short. This was a great chance of getting a big stack.