Take a look at the original sentence again:
No foot powder, no shoe insert, no expensive soap can kill the odor of Bartholomew's
feet, when he takes off his shoes, even
the goldfish gag.
You chose to fix it the correct way:
No foot powder, no shoe insert, no expensive soap can kill the odor of Bartholomew's
feet. When he takes off his shoes, even
the goldfish gag.
No foot powder, no shoe insert, no expensive soap can kill the odor of Bartholomew's feet is a complete sentence. When he takes off his shoes, even the goldfish gag is the second complete sentence. You are always correct when you use a period between the two complete sentences that create the comma splice.