Decisions, decisions!

Vulnerable, righty opens 2S (weak) and I hold:

N

North

♠

107

♥

Q82

♦

AQ32

♣

Q1075

Do I come in? Even though they're vul and I'm not, I passed.  Right decision?

East passes and partner who holds a 11 point balanced hand with four spades also passes. So, now, I had to lead.  What would do you choose?

I chose a spade, partner encouraging. Click "Next" on the diagram below to see the defense; can you spot the misdefense?


It was at this point:

I led a club at this point, but the only winning return is a heart.  It is clear that I should not lead diamonds because partner needs the king of diamonds as a safe escape card.  But why hearts over clubs (partner has not had a chance to signal suit preference)?  The club holding that I'm hoping for from partner is AJ.  If I lead hearts, I'm hoping for A10 with him. Which is likelier?  How does one tell?