For entry into Schedupe C, Do I add in total dollar amount collected including MI sales tax (that I subsequently sent to the State of MI) or w/o sales tax paid to MI?

Yes, report total income (including sales tax) in the income section of the Schedule C. Then make sure to also include the total sales tax as an expense in the expense section. This will ensure that you don't pay taxes on the sales tax you remitted to your state revenue department.