If I work a full time job where more than 99% of my income comes from, should I still use Self-Employed since I had a very small income through Amway?

If your income from Amway was less than $400, you can claim it as Miscellaneous income instead of Schedule C self-employment, because you will not owe any self-employment tax on a profit of less than $400.  You cannot deduct any related expenses this way.