The previous answers are excellent examples of solutions to the problem.
As a newcomer to the conversation I’ll summarize the learning opportunity here.
In any complex CAD model in any CAD software, it is very important to learn the skill of working with calculation-heavy models without wasting time waiting all day.
As Joseph mentioned, you can temporarily disable all or part of the model. Disabling the entire solver is an easy way to make adjustments. Another way is to disable the troublesome component manually or by addition of a “data dam” component just upstream of the killer component (SDiff in this case), so the componenet doesn’t calculate until you press play on the data dam, but everything upstream of the data dam will calculate as normal.
My first though was as Birk mentioned, which is to work with the square count greatly reduced, until you are ready to be patient for the full calc, then jack the square count back up and/or click play on the data dam.