Using a measure as if it was hardcoded for a multiplier

if it's a different date field in a different table (but there's a relationship between these two tables) you may find that the filtering you're applying on one table is feeding through the relationship you have, causing a 'correct data' filtering with what you're trying to display but a wrong outcome for you.

Is it possible to count the open eligible accounts (or sum whichever formula)? 

It would be something like the following:

Expected Account Renewal = 

VAR __EligibleAccounts = CALCULATE(COUNT(Table1[ID]), FILTER (Table1, Table1[ID] = Table2[ID]))

RETURN
__EligibleAccounts * [Account Renewal Rate T3M]

You can create a custom column with the variable as well which you could use to show the values next to the measure. You should be able to replicate the [Open Eligible Accounts] column inside of your other table. The __EligibleAccounts would need to flex between count/sum/countrows depending on your data requirements.

This method would ensure that you're not being hindered by a relationship issue because you're consolidating the data into a singular table, and then you can explore changing your filtering options.