Repeating Macro Column By Column Until It Hits Blank?

This is for a template for teachers to analyze student testing data. On sheet4, wrong answers in each column are noted by a lack of a + in the corresponding cell. I want to paste the names of the students who missed each question into sheet 5.

I've done it by repeating a filter macro, but I manually copied the following separately for the 75 columns in the template.

Problem #1 - there must be a more efficient code, something that automatically loops to the next column

Problem #2 - the template has 75 columns, but many tests have fewer questions. I'm trying to find a way to stop the loop whenever it hits a blank cell in Row 10 on sheet 4. I've done it with an if/then in the last section on the above code, but where I'm at now, i would have to add that to the code section for each column. Which isn't that big a deal, but I figure there must be a better way.

The relevant portions of the workbook are attached here.

repeating macro until hits blank cell sample.xlsm