Don't choke!

Last round of the local club game.  You don't know it, but you're
battling for first and second.  An average round will sew it up.
Don't blow it!

(Scoring is matchpoints in case I hadn't made it obvious.)

Board 4 (both vul)

3
K1084
AQ74
KJ104

Partner deals and opens 1D.  RHO comes in with 1S.  You double, but
LHO bids a natural 2H anyway.  Partner passes and RHO rebids 2S.  Lots
of bidding for the points you're looking at.  What's your next move?
If you try 3S, partner responds 3NT.  Anything to add to that?

Board 5 (opps vul)

Dummy
K10764
KQ104
10
J52
                   AQJ5
  xx             J5
  xx             96
                   A8763

Your LHO deals and opens 1D.  1S from RHO and you interject with 2C
(no cringes from the audience please!).  LHO rebids 2D.  RHO scrapes
up a 2H bid somehow but passes when LHO bids 2NT.

Partner dutifully leads the club four.  You win the ace and return the
suit, but partner pitches a heart and dummy wins the jack.  Declarer
leads the diamond ten from the board and it holds the trick.  Declarer
now leads the king of hearts.  This rides to partner's ace, whereupon
partner switches to the nine of spades, to the ten and your jack.
Your lead.

Board 6 (your side vul)

K9532
3
KQJ96
109

You deal and pass (or do you?).  Partner in third seat opens 4H.  RHO
comes in with 5C.   Anything to think about here?

Bonus problem (still matchpoints):

A                   KJ104
KJ                 AQ104
108643         KQ92
AKJ42          Q

1D                1H
2C                2S(4SF)
3C                3D
?

Agree so far?  How should the bidding proceed?