PWM of 2.8v LED input (high-side driver IC selection)
Your existing module, according to you, meets all your needs but the voltage is simply too high. Presumably these LEDs require a 2.8V input voltage that for some reason needs to be low-resistance. It is hard to speculate without knowing the equivalent circuit for the LEDs, but based on this requirement it sounds like you can rule out being able to use a simple resistive voltage divider here.
The best solution I can think of would be to either use a high power op-amp (which is unnecessarily complex here) or simply drive it with a FET. An FDN337N FET would do nicely.



simulate this circuit &ndash; Schematic created using CircuitLab
Alternatively if you want a slightly simpler setup with few unknowns you can also use a solid state relay, they can handle the current and can switch fast enough to handle PWM.