Sorry I may not fully understand your question.  But if you did not mark any of the income or expenses as T or J, they'd be presumed to be jointly held and split by half on the worksheet.  Wages, for example, would be one of the exceptions where it's linked to either the taxpayer or the spouse and would not be split except for community property states.

If you believe the 50/50 split is not correct, you can go back to the input screens to code these correctly for T/S/J.

The worksheet already shows you the comparisons for separate vs joint filing not only in terms of income and deductions as well as credits but the bottom line for tax liabilities.  It's not perfect as there are some quirks that Lacerte couldn't work through for MFS (e.g. DBC benefits exclusion) but it should be pretty close.  You shouldn't have to split the numbers and prepare separate returns to compare - that's the whole point of this worksheet.