Couple of thoughts:

1) At NL10 I don't think turning 99 with a spade into a bluff is a great idea (especially if you were targeting villain in this spot after 100 hands only which is small sample). While you may puke with AK/AQ here villain may always snap/ unless you have seen this player fold to pressure with a well defined range of TPGK/TPTK on rivers.

2) I don't know what your 3-bet flat strategy here is from UTG, but I assume that 99 is towards the bottom of your range. So the question becomes would you take this exact line with flushes (e.g. KQss)/FH/quads here? I would expect that the population would frequently x/r with set combos on flop along with some FDs. So if you get here with this exact line with too little value hands, we run the risk of becoming unblanced and villain can start calling super wide. Furthermore what are you doing with TT and JJ here? Would you rather turn JJ or TT with a spade into a bluff here or 99 with a spade (does villain ever have QJss, KJss, QTss, etc.). If you are super confident villain is capped at TP here then it becomes irrelevant as none of these combos block TP (except maybe JJ if villain ever has AJ as a 3-bet) and using spades for a balancing factor is a good way of preventing overbluffing as long as you are balanced.

3) You can do a minimum defense frequency here of 24 AK, AQ combos here against your jam to see how often villain should be calling with only TP type hands. While it is a good exercise, as mentioned above I don't think taking this line at NL10 is a great idea.