Let's forget about what happened in the hand and work this out logically in a hypothetical game where everyone is competent. Becuz what we really wanna know is how to play this spot well, not how not to get euchred in one particular hand.
Ok here's what we can deduce right away:
S2 can't have AcJc or Jc9c becuz he would've called in the first round with that hand. S2 can only have Ac9c, or just the Ac or just the 9c.
S4 can't have two clubs becuz he would've ordered in the first with 3 and for the same reason he can't have the Jc. S4 can only have just the Ac or just the 9c.
So S2 is the only opponent who can possibly have AcXc, being precisely the Ac9c. Against that hand it doesn't matter what you lead between the Qc or the Tc on 3rd street. Your last club will be boss either way. Same is true if S2 has just the Ac. Same is true if your P has the the Ac (If you lead the Qc and your P has the AC, the only player who can have a higher club than your TC is your P if he has the JC). So it doesn't matter what club you lead EXCEPT those times the Ac is buried! In that case you'd want to lead the Qc. So since in the former case (Ac not buried) it doesn't matter which club you lead, but in the latter case (Ac buried) leading the Qc is best, always leading Qc is the unequivocal best play. I.E. leading the Qc strictly dominates leading the Tc after your opponents turned down the Kc.
Ok, so we got that part settled. Now what do we do on 3rd street. Should we lead our boss trump or lead the QC. First lets talk about the other trump that's still out in the wild, the QD. Based on the play of the hand it is perfectly logically possible for S2 and you P to have the QD, but we know S4 can't have it becuz if he did he would not have played the JD on 1st street. What this means is there is a 33.33% chance S2 has the QD, a 33.33% your P has it, and a 33.33% chance it's in the kitty. Notice if you lead the Qc on 3rd street you will score a point at least (33.33 +33.33) 66.67% of the time regardless of whether your P has the AC or not. If your P has the QD, you preserve your point by not cleaning out his trump. If the QD is in the kitty, leading the QC will promote your TC to boss status those times your P does not have the AC and then you'll get the last 2 tricks.
This is worth repeating. When you lead the QC on 3rd street you will score a point at least 66.67% of the time regardless of whether your P has the AC or not. That number is also independent of whether your P has the AH/boss equivalent or not. Obviously when your P has the AC or the AH or perhaps even both that percentage goes up significantly. And also keep in mind even those times S2 has the QD your team has many ways to escape. For example, say you lead your QC on 3rd street and then S2 trumps in with the QD. Great, your team is guaranteed the point now as you'll have the boss or effective boss club + the remaining trump for the last 2 tricks. Or say you lead the QC and S2 takes the trick with the AC, and S2's last two cards are the QD and a non-boss heart. If your P has the boss heart your team also scores a point in that scenario.
So we know that leading the Qc on 3rd street will make a point somewhere north of 66.67% of the time. I highly doubt leading trump on 3rd street and putting virtually all our eggs in the club basket on 4th street, potentially losing control of the hand when one of our opponents has the AC--making 5th street a free for all--will do better than that number. But let's try to find out.
Ok lets do some combo counting and try to figure out the probability S2-S4's team has that AC before S1 makes a move on 3rd street.
S2: First if S2 has the AC he can't have the JC as he would've ordered, so S2 has: 1C1 x 1C0 x 10C2 = 45 combos of hands that include the AC.
S3: 1C1 x 11C2 = 55 but we have to subtract 1 combo since S3 can't have AcJc9c as he probably would've ordered in the first round. So 54 combos
S4: If S4 has the Ac then he can't have another club as he would've presumably ordered with 3 in the first round. Also as mentioned, S4 can't have the QD. So S4 has: 1C1 x 2C0 x 1C0 x 8C2 = 28 combos of AC hands
There are also 55 combs that include the AC in the kitty.
Total combos here are 45 + 54 + 28 + 55 = 182. This number is somewhat less than the amount of combos in a random distribution (12C3 = 220) that's becuz we made hand reading/logic adjustments above eliminating certain hand combos that can't or shouldn't be there.
So S2 will have the AC 45/182 = 24.73% of the time
S3 will have the AC 54/182 = 29.67% of the time
S4 will have the AC 28/182 = 15.38% of the time
The Kitty will have the AC 55/182 = 30.22% of the time.
Ok so (29.67+30.22) = 59.89% of the time the AC will be in our P's hand or the Kitty and thus 40.11% of the time it will be in enemy hands. This means if we lead trump on 3rd street our team will make a point at least 59.89% of the time. 40.11% of the time we will lose control of the hand on 4th street when our opponents have the AC and then 5th street comes down to luck of the draw.
So leading the QC on 3rd street gets our team a point somewhere north of 66.67% whereas leading trump gets us a point somewhere north of 59.89%.
Conclusion: When it is still possible for your P to have that last trump, and when your offsuit lead is virtually guaranteed to create a boss offsuit, DO NOT LEAD trump. Leading your offsuit is best and as already discussed, leading the QC is better than the TC.