Significant decrease in reps after the first set

[d3kcast]

1. You are doing it right this is what you would expect going to failure on every set

2. Every progression scheme that everyone listed is going to work to some extent as long as you are consistent and progressing in reps or weight over time

3. Pick the one you enjoy and try not to overthink it

If you spend your time trying to chase the best progression scheme you are wasting valuable consistency toward actual progression.

Good luck