Flop stab is the money-maker here; once we skip it, the turn bluff with total air is a bit too loose and river check is fine.
On KQ7hh in a limp pot, SB’s check caps them quite a bit and we can apply pressure with a small stab. Using T4o as a flop bluff is attractive because we have no showdown and plenty of better hands to check. Skipping the stab is a small missed chance to pick up dead money.
Note: Losing value by not taking a cheap flop stab in a great spot to bluff after SB checks a wide, capped range.
After flop checks through, the Ad is great for our perceived range, but SB’s limp-call range still contains a lot of Ax and sticky Kx/Qx. Firing turn with total air and no blockers is marginal; we’re bluffing into a range that’s stronger than ideal and not blocking many continues.
Note: Turn bluff is a bit too loose with zero equity and no relevant blockers versus a range that likely includes a lot of Ax/Kx/Qx and hearts.
When the 5h completes the flush and SB calls turn, their range is very heart-heavy and pair-heavy, while we still have a lot of strong value in theory. Giving up and checking river is correct; blasting again with T4o and no heart would be spewy.