Welcome, I am Chris (aka-Moose)
The low fluid could of caused the ABS and brake light to come on, and you may still have a brake fluid level issue if the reservoir level sensor is faulty. We need to get the brake pedal to feel right by completing the rear bleed. It looks like you have a restriction in the brake line, faulty ABS HCU, or faulty master cylinder. We need to open up the line to the rear brakes prior to the ABS to see if you can get fluid pressure there. If so then after the ABS try there.
----------Once you get an answer----------
1) Please realize I base my info requests and answers on what you type.
2) The more you can tell me the faster and better I can help.
3) I am not an employee for Just Answer, they pay me nothing to help you.
4) I am paid by the customer from your deposit, but only when you rate my answer.
5) You will notice it says rate to finish, rating does not close the post, or end our conversation.
6) I am going to stay in contact with you until you respond and tell me your happy or pleased with the answer. So please reply and let me know the progress on the issue and our discussion or if more help is needed.