50NL river bluff

Villain's about 40/28/7 over 30 hands, not got to showdown either so obv not too much to go on. First time it'd been folded to him in SB so i've no idea what he's completing with. Was gonna bet any non 7,Q or club river. Wasn't expecting the donk but i think it turns his hand face up? Or should i just get down from my tree branch and stop chucking my poo around already:)

PokerStars No-Limit Hold'em, $0.50 BB (5 handed) - Poker-Stars Converter Tool from FlopTurnRiver.com

SB ($47.30)
Hero (BB) ($51.20)
UTG ($52.80)
MP ($6.05)
Button ($83.65)

Preflop: Hero is BB with 6http://www.flopturnriver.com/phpBB2/...es/diamond.gif, 7http://www.flopturnriver.com/phpBB2/...es/diamond.gif
3 folds, SB calls $0.25, Hero checks

Flop: ($1) 4http://www.flopturnriver.com/phpBB2/...es/diamond.gif, 8http://www.flopturnriver.com/phpBB2/...miles/club.gif, 10http://www.flopturnriver.com/phpBB2/...miles/club.gif (2 players)
SB bets $1, Hero raises to $4, SB calls $3

Turn: ($9) 2http://www.flopturnriver.com/phpBB2/...es/diamond.gif (2 players)
SB checks, Hero bets $5.50, SB calls $5.50

River: ($20) 3http://www.flopturnriver.com/phpBB2/...iles/spade.gif (2 players)
SB bets $10, Hero raises to $41.20 (All-In)

I dont understand it, but I think it's neat

usually raise preflop, usually call flop, check or bet more on turn, river is good; he seems quite weak/empty