Wow, what a trooper and strong person you are for going through all of that.
First off I want to send you and your mom a HUGE cyber hug.
Second. Stop and take a moment. Take a deep breath. Your an amazing young person.
You can only do what you can do realistically. Over working yourself is not the answer, you can't help your mom out if your burn yourself out and don't take care of yourself first.
Self care in times like this may feel very selfish but in the long run are what make things happen. If you need to hop on the internet after a long day of working to help provide for your family and your father agreed to pay for that and nothing more I see no problem with him sticking to his word.
If your talking to people on this site helps clear your mind and give you better perspective on home life problems or horse related and helps you decompress own it and don't think of it as a bad thing.
You are only human. You can only do what any other person can do.
I too have been in the position of caretaker to a single parent and being the one with the only supporting job. It is not an easy task physically or emotionally. Know your such a strong caring person to be able to do this. This day in age so many people would have turned down a wrong path or not helped in the ways you are or altogether split from both parents and said deal with this on your own. But you didn't.
Know your mom is beyond grateful for all that you do even if she doesn't say it. A child's support and love and understand without judgement is more then any parent can ask for and your doing just that for her! Its priceless and so wonderful!
As for your father, I can somewhat relate. I am adopted and found out this year in meeting him for the very first time that I was the result of the divorce of his first wife from my eldest half sibling, that I was the result of the affair my father had.
In time you can only hope your relationship with him will lesson in stress and awkwardness. You can only do your half and have high hopes and low expectations for anyone else.
Again Hugs, Know I one person on this site that has more then enjoyed fallowing your threads, viewing your photos and listening to your successes in life!
I hope you stay with us and that what ever is meant to be is meant to be and works its self out without hurting your anymore!