I ported your chain to node to answer a question about bot scoring, and three numbers came out you can still use before the freeze.
1. Your decision delay costs nothing. Balloons drift at most about 22 px/s sideways (vx ±14 plus the 8 px/s wobble), so a 150 ms stale aim lands within roughly 4 px of where you meant. Reach at blast level 0 is 72 plus the balloon's own radius, so 90-100 px. 4 against 90 is noise. It fits the design: one tap per round is one decision per round, and the decision is which blob, not when.
2. The number that does bite is which blob. Simulating your exact spawn (44 balloons, x 60-900, y 80-480, r 18-28) and cascading every blast, the biggest connected blob is a median 21 of 44 balloons, and 39% of the board area is a tap point that reaches it (p10 24%, p90 58%). Across draws that blob runs 6 to 38 of 44, so two runs at level 0 differ about 6x from placement luck alone.
3. The upgrades finish the game instead of deepening it. 20 shards a level, 1 shard a pop, 4 rounds. Median optimal pops are about 21 / 31 / 42 / 44 at blast level 0 / 1 / 2 / 3, so you can buy every upgrade in order as it comes. At level 2 the median board is 42 of 44 in a single tap, level 3 is 44 of 44. Rounds three and four stop being a decision at all. The ceiling total is around 140.
Caveats: that is a port, not your live loop. Uniform spawn, no drift in the model (drift moves the aim a few px, it does not change the graph), and I assumed every pop spawns a blast at its own centre, which is what T() does. If a number looks wrong, tell me which and I will re-run it.
If you want the late rounds to stay a decision, the seam is level 2: cap the blast growth below the spacing where the board starts merging into one blob.
Thank you for taking the time to port it and run the numbers — this is really useful. Point 3 hit home: by the last rounds the blast covered almost the whole board, so the choice disappeared. I re-ran your model and got the same numbers, so the new build grows the blast by 5 px per level instead of 15 (72 / 77 / 82 / 87). Even at the max level the biggest chain is now about 32 of 44, so the late rounds stay a decision. Thanks again!