*Range charts made with https://premiumpokertools.com/equity-calculator
Here's my analysis! Assuming your opponent is min-raising about 80ish percent of hands preflop, a reasonable calling range against your small 3-bet size might be this:
After the flop, removal effects make villain's range look like this:
When you shove 3.5 times the flop, the villain's minimum defense frequency is 22%. If the villain only calls 2-pairs (18 combos), straights (20 combos), and flushes (15 combos) they're already at that 22%. Generally bet sizing is about finding a size that puts your opponents range into the most awkward spot, and this 3.5 x pot size doesn't do it here since they can call pretty comfortably with the above 53 combos. Villain might also reasonably call with AsJx with good equity and the nut-flush blocker too. If they call wider than I estimated preflop and need to defend wider, then KxTs, QxTs, JxTs could make reasonable bluff catchers too.
For these reasons, I disagree with your statement "My reasoning is : If I were my opponent, I would not have called unless I had Ace of spades (and probably another spades)". If you play this way, you will almost certainly be over-folding in these spots. Villain could (and probably would) call wider than this. Even if you have a read that the villain plays too tight, a smaller bet size (50% - 75% pot) would probably get an overly tight opponent to over-fold here.
Another caution (though not necessarily a mistake!) I would make here, is with the particular hand that you chose to bluff with. When you shove 3.5 x the pot, we know that your opponent doesn't have to call you with anything worse than 2-pair. That means your value hands are most likely going to be sets, straights, and flushes (9 combos of sets (KK, QQ, JJ), 16 combos of straights (AT), and, say, about 25 combos of flushes (suited aces, low suited connectors and gappers). That's about 50 hands for value. Your value bet to bluff ratio should be 9:7 (close to 50:50) given your overbet size. I'm not entirely sure what your range might look like here, but before bluffing aces I might look to bluff hands with a spade and a good blocker (As, Ts, maybe 9s) since you make it less likely that your opponent has a flush or the AT/T9 straight, and in case you do get called by a lower flush or a straight, you have a redraw to beat them. If you agree with me here and do bluff with these spades, you'll just have to be careful not to bluff every ace you have too, since you'd probably be over-bluffing.