Will my line run if I lower the maximum average CPM to match the forecasted average CPM?
It might not. The forecasted average CPM is calculated based on the current criteria that you set. If you edit strategy parameters, then the forecast may change.
If you want to see how a forecast will change if you alter the maximum average CPM, then set a new limit and click Show forecast. The forecast will be recalculated based on the new criteria.