Be careful about jumping to conclusions. The more carefully l look at your model, the more questionable methods I see. In general, solid Boolean operations are to be avoided as much as possible. There are many hidden details about them that affect speed and quality of results.
For example, I just increased ‘Step width’ to 3200 by the “quick” double-click-to-enter-value method and the Profiler time on SInt jumped to 1.8 minutes 
None of our discussion accounts for that! The problem now is the extruded ramp shape is very weird somehow, altogether a different issue than data dams or other means to avoid slider delays.
I assure you that there are other ways to construct stairs that are far more responsive to sliders. I’ve done quite a few spiral stairs myself and seen others do them. Here is one, for example:
You can say “my stairs are different” and that is true. But I’m pretty sure I could make your kind of stairs from the above without the sluggish response you are seeing. I’m not willing to do that work right now but you need to know that there are other ways that are quicker than what you posted.