Greetings! I have some tax questions that need answering.

#1
I have recently just got into serious trading. My main source of income is mine and my fathers IT consulting business atm. I make around $3500 a quarter give or take. I have made some profits since starting this year and will need to pay short terms gains tax. However understanding how it works is baffling me. I have several questions that need clarification. If anyone has a good and simple tax guide for this sort of stuff it would be much appreciated. Based on 2019 tax brackets:

#1: Are gains taxed accumulatively or are they taxed individually - meaning if I made two trades and one trade nets $10,000 (12% brkt) and another nets me $74,201 (22% brkt),
will I pay each individually $1,200 and $16,324 respectively or is it accumulative for a total of $84,201 (24% brkt) and I end up paying $20,208 in short terms capital gains tax.

#2: I read somewhere that you have to add that income to your individual income as well. So, say I make 14000 this year and net $6000 in short term gains. Does this mean that I have to add that to my regular income and report $20,000 and pay taxes on top of the short term gains? So instead of owing the progressive tax of $1,486 on my regular income before adding the gains, I would end up paying $2,206 and an additional $600 of STG tax for a total of $2,806 - is this correct?