top+bottom pair. How to play?

Allain is a calling station and he makes wierd bluffs. Rivered most of his winnings. The pot before this one he lost over 30$ so I think he might be on tilt. I'm raising with K4 just to vary my play. This is the first hand I'm raising in 35 dealt hands. My image is like a rock.

Party Poker No-Limit Hold'em, $ BB :#A500AF(Allain)/ (6 max, 4 handed) converter

Hero ($26.61)
SB ($40.93)
BB :#A500AF(Allain)/ ($39.27)
UTG ($0)

Preflop: Hero is Button with 4[img]/images/graemlins/diamond.gif[/img], K[img]/images/graemlins/diamond.gif[/img]. SB posts a blind of $0.10.
<font color="#CC3333">Hero raises to $1</font>, <font color="#666666">1 fold</font>, BB :#A500AF(Allain)/ calls $0.75.

Flop: ($2.10) 3[img]/images/graemlins/spade.gif[/img], 4[img]/images/graemlins/club.gif[/img], K[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(3 players)</font>
<font color="#CC3333">Allain bets $1</font>, <font color="#CC3333">Hero raises to $3</font>, Allain calls $2.

Turn: ($8.10) 5[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(3 players)</font>
Allain calls $35.27 (All-In)

Whats your play here? I've never seen this guy played anything worse than two face cards when there is a raise in front. But he bluffs alot. Its almost impossible that he called my (low?) raise on flop with a gutshot straightdraw. Can he have a set? What would you do?

[Spladle Master]

I'd get more in on the flop and definitely call the turn.

Party Poker No-Limit Hold'em, $ BB (6 max, 4 handed) converter

Hero ($26.61)
SB ($40.93)
BB ($39.27)
UTG ($0)

Preflop: Hero is Button with 4[img]/images/graemlins/diamond.gif[/img], K[img]/images/graemlins/diamond.gif[/img]. SB posts a blind of $0.10.
<font color="#CC3333">Hero raises to $1</font>, <font color="#666666">1 fold</font>, BB calls $0.75.

Flop: ($2.10) 3[img]/images/graemlins/spade.gif[/img], 4[img]/images/graemlins/club.gif[/img], K[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">BB bets $1</font>, <font color="#CC3333">Hero raises to $3</font>, BB calls $2.

Turn: ($8.10) 5[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(2 players)</font>
BB bets $35.27 (All-In), Hero calls $22.61 (All-In).

River: ($65.98) T[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(2 players, 2 all-in)</font>

Final Pot: $65.98

Results in white below: <font color="#FFFFFF">
BB has Kc Tc (two pair, kings and tens).
Hero has 4d Kd (two pair, kings and fours).
Outcome: BB wins $65.98. </font>

[Spladle Master]

[censored] happens. Next hand.