It looks like you have two Black Suit losers and so need to bring home either the Clubs or Diamonds without losing a third trick.

Bringing home the Clubs needs them to split 3-3, a 33% chance, so the Diamonds look a better bet as they only need to split 3-2

If you ruff the ♠ K you may run out of entries if Trumps don't behave so a a better line is to throw your singleton Club on the ♠ K

The you can play ♦ A, ♦ Ruff, Club Ruff back to hand, ♦ Ruff with ♥ K, back to ♥ A Q J and then cash your Master Diamonds bringing home 11 tricks

You lead a low Spade. You do not lead another Diamond! You want to attack Diamonds but North must be the one to continue the attack so that you play after Declarer (who has the ♦ K)

As soon as Dummy went down you counted their 9 points, added your 9 to make 18. Declarer's 1NT bid has shown 12 to 14 of the remaining 22 so partner has between 8 and 10 points.

Partner won't have the ♦ K (or they would have played it on the 1st round). Declarer has attacked Clubs so probably has all of those. That means partner's points are in the Majors.

Better to lead a Spade as you are leading through strength and leading a Heart may just give a trick away.

You draw two rounds of Trumps (both declarers follow) then you must switch to the Spade finesse before drawing the last Trump.

This is because you need to keep the ♥ 9 to ruff the inevitable third Club if the Spade finesse loses.

You can then draw the last Trump and Knock Out the ♦ A having preserved Dummy's last Heart to stop the Club Suit