Right or Wrong?

I had a very interesting play problem come up in the NAOP. It was the final day and we were playing against one of the best pairs in the room. We had a great game going and I thought we were probably qualifying at that point but there were still about 8 rounds left to play. I was in 3N with these two hands:

KJT93
82
J97
QT3

AQ2
AQJT
QT2
A42

The auction was 2N p 3N. This is a typical "insane" matchpoint auction for us. LHO leads the ace of diamonds (asking for attitude). RHO plays the 6. Now LHO returns the 8 of diamonds, I play the jack from dummy and rho plays the 4. What next?

We have 5 spades, 1 heart, 1 club and 1 diamond. The obvious thing to do would be to finesse the heart and then try finessing it again. But what was the 8 of diamonds? It was a suit preference card indicating a heart card. I honestly believe the least falsecarded signal is suit preference, even though my LHO is a very strong player I took it to probably be a true card. I was also confident that if he had 5 diamonds he certainly had a king. Good players will almost always lead small from AKxxx if they have no side entry. If LHO has 5 diamonds and the heart king he will be strip squeezed on the run of the spades.

I thought for a long time and decided to run spades. LHO started with 2 spades and pitched a low club (encouraging) followed by 2 low hearts. RHO pitched 2 low clubs (encouraging). From my hand I pitched a heart and a club. This was the end position:

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82
9
QT3

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AQJ
Q
A4

If LHO came down to the guarded heart king and started with 5 diamonds, that only left room for one club. In that position my winning line is to cash the club ace and get out a diamond (see why I didn't pitch a diamond from my hand?). Given that I believe the diamond 8 this is the most likely layout. However, I had a lot of extraneous things to consider.

• Did LHO stiff his HK and hold on to 2 clubs? This was possible to do in tempo since I took so long to play. I didn't think it was likely because of another pattern people seem to have. When they figure out early on in the play they need to stiff their king, they do it immediately. I'm pretty sure if LHO wanted to go that route he would pitch heart, heart, club in that order.
• Did LHO falsecard the D8? If he had the club king and the AK of diamonds, looking at 7 points in dummy and 20-21 in my hand he knows partner has very little. A falsecard is very possible, especially since even if his partner does have an entry like the queen of spades, LHO has a slow entry not a quick one so it's not that important. However, again few people falsecard suit preference and it's important to remember not to give your opps too much credit.
• Did LHO start with 4 diamonds all along? With AK85 he might have chosen to lead a high diamond then had nothing better to do but continue. In this scenario he might have chosen a different lead (a major is preferable on this auction) and he would need the 5 to know that playing the 8 is safe.
• If LHO does have xx Kxxx AKxxx xx like I think, what will happen to 4 spades? That is the field contract. LHO will lead 3 rounds of diamonds and his partner will ruff and lead back a heart. The clubs then go away on the hearts, so I'd be down one. So even if I go down 1 in 3N I will get an average.

At the table I decided the first 3 inferences were strong but not sure, maybe 80 % each. However, when combined that makes LHO having the hand I think he has to only be a 50/50 shot. If the heart hook is on or diamonds are 4-3, I'm going to get a good result for playing in 3N if I just finesse now. I decided the risk wasn't worth it and I hooked a heart and went down 1. Sure enough we got an average board, and making would have been a top. LHO did have 2452 with the HK.

Looking back on it I'm not sure if I did the right thing. Very often I will play a hand to have a guess in the end position and then back my judgment about the layout 100 %. If I was playing my A game and was feeling very confident I'm sure instead of thinking my inferences were 80 % I would have thought they were 100 % and gone for it. I felt bad for not backing up my judgment in this case because it is one of my strengths in declarer play. However, we did get an average and we did qualify for the nationals. Had I gone for it and gone down for a zero, we wouldn't have qualified. From that point of view I did the right thing.

I still don't know, I'll let you guys decide.