In other words if my total income was under 12.4k but I earned several thousand being self employment still, do I not have to pay any income tax taking a standard deduction? Or...do I only have to pay 15.3% self employment tax and get to skip the personal income burden?
you are correct - you would have to pay the 15.3% and there would be no federal income tax - not sure what your state requirement would be though.
The above answer assumes you are not and CAN not be claimed as a dependent by someone else. A person who qualifies as a dependent doesn't automatically get the full $12,400 standard deduction. A dependent's standard deduction is $1100 or his earned income + $300, but not more than $12,400.
Unemployment compensation is not earned income for that calculation. So, for example, if you had $11,000 of unemployment, you would have to pay federal income tax on $9900 (11,000 - 1100 = 9900).