Life is cruel, but only if you don't do something about it.
I believe you've created a previous topic about this. We're here to help. Many of us have been in similar predicaments, and even worse.
Here man, let's break this down...
-Don't worry about having a car, it's quite expensive these days, and frankly, there's a lot of people who don't have cars. I was recently in an accident, and have no car as it was written off, and my insurance is too high right now. I too, live in the middle of nowhere. If you have to ride a bike to work, it's exercise, and transportation. Every time you go to work you're getting in shape.
-As of now, push aside the things we'll work on later, and focus on the present. Don't worry about your son, or karate master, or your ex. Doting on your son isn't going to help your emotions in this present time, neither is thinking about your ex, and karate-master.
-If you have a job, then you have income. If you don't have a job, then get one, anywhere.
-For finance, find things that are costly in your bills, and deal with them accordingly. Depending on how much of a change you want, you could cancel your TV, and be conscious of heating & air conditioning usage.
-Once you build up money, I would suggest moving into the city, and finding a job right before you move, so you're set, as soon as you arrive. Living where you are now, with no vehicle is not going to help in the long run. It will help in the short run if you find a job you can ride a bike to, and use this job to help you move in to the city where life will then become easier.
-From there on, you're in a new place, in the city. You have income, and you can sarge. All of this sarging experience you wanted, you now HAVE. Remember that PUA is not only about building female relationships, but is also about building relationships in general. You can meet many new people, new friends, hang out, and do things.
-Eventually you WILL be a master at this. I have a lot of faith in you, and know you have potential. All you have to do, is turn your life around, and use it.
-From there on out, you will eventually have friends of both male and female, a girlfriend far more attractive than your ex (no offence, if any taken).
If you see where I'm going, you WILL have an amazing life. Karate-d1ck will envy you, while your ex is jealous. Your son will only find the "Karate Master" part of that man cool until he grows a bit older, and realizes that his Dad is a stud, with a fun and exciting life and wants to be with you more.
Also remember that anything could happen at any time. Your ex could break up with him for any reason, etc.
In Conclusion. You have to step up, take the plate, and make it happen. I've already given you steps to follow. Some may not be easy, but every struggle ALWAYS, and I mean ALWAYS leads to a pot of gold in one way or another.
You always have brothers here man. I'll PM you my personal email in case you ever have questions of any sort.