When a bulb is listed at a certain planting depth, it can probably be varied by 40% or more one way or another without killing it.

In a drier location, I intentionally plant bulbs 1/4 deeper than listed because the soil stays moist down deep, so they perform better. I also plant bulbs deeper if they are marginally hardy in my climate to protect them from the cold.

I would not worry about the mulch. I have seen little tiny crocus bulbs push through not only mulch but dense perennial ground covers that were 3-4 inches thick, and leaf out and bloom above that with no problem.

Thanks for the info!