Pass. It kills me to let the opponents play in their 8-card two-level fit, but what else can I do? Maybe I would have bid with my partner's hand; we'll see later.
K. This is an auction on which to make a safe lead. This isn't completely safe (for example, dummy could have Jxx and declarer the ace). Still, it is safer than anything else. A trump from xxx would be okay, but from J10x is risky (partner could have a singleton honor).
3. Partner discouraged in diamonds and is unlikely to have the jack or ace. Declarer could easily be holding up with AJx. So, it is a big mistake to continue diamonds. Clubs and hearts are still as dangerous as ever. Now that you see the trump layout, a low spade has to be safe. Even if partner has a singleton queen or king, it won't cost. Neither will it cost if he has a doubleton queen or king. This flat, useless dummy screams for a passive/safe switch. These are the remaining cards:
As you can see, anything but a spade would have been costly. A diamond would go into the AJ (no surprise). A heart or club would be a huge help to declarer, costing the defense a trick. Below is the full deal:
Would I have acted in direct seat with the East hand (over North's 2)? I confess that I would not have. If you end up defending 2 on this deal and letting it make (-110, or worse, -140), get used to having 40% games. With accurate defense, you will likely set the contract.