You've got a 4th trump, an ace and a doubleton. This is far from a mimimum hand. I'd accept partners invitation and raise to game without thinking twice.
1♥ is obvious to me. Double is not an option to me - I'll never be able to descirve my hand afterwards, 2♣ neither. And I'd never bid 2NT with these spades in hand....
a) Prefer 3♠ as forcing (slammish) c) Prefer 3♣ as 55 GF d) I play 3♥ as NF inv e) 2♦ is GF for me f) 2♦ is GF for me, 3♣ is natural with 4-4 (or 5-4). I don't play NMF, rather the xy-NT (a kind of 2-way NMF). I prefer jump rebids by responder to be strong and all invites to go through 2♣.
I might convert the second double if on lead.... maybe. And lead a trump. I'd not even consider this here. I'm passing now. If this is enough for game, partner would have bid it already.
Disagree with Whereagles. 2/1 followed with support shows 3-card support for me. Splinters are limited. 2NT therefore is unlimited with regards to strength, a little less when it comes to distribution.
I most probably wouldn't have rebid 3♣ with the north hand, but I'd not fault anyone for making it - it's mostly a style question IMO. Rebidding 3NT is bad, 4NT worse - 4NT is definitely to play.
The shape is all wrong??? Basically you promise 3 card support for any suit partner has. I would X with 6 HCP fewer and the same shape. I guess he replied before the OP was edited and the hand put in..... B)
That depends on their agreements, doesn't it? If 3♥ is indeed a splinter in their methods, the only "misbid" is 4♥ (if they play italian style cuebids). So we can't tell if there's any fielded misbid unless we know their methods.