Fight for your marriage by all means necessary if that is what you want, BUT if that is your strategy you have to realise that begging will do more harm than good. When you beg, you send a sutble message that you CANNOT live without your partner, come across needy and desperate and non capable. And what decent man really wants that?
If you're going to fight you need to be clever about it, so that if it fails you can walk away whilst keeping your head high and with your self respect intact.
Right now you are panicking - not a good emotional base for working on anything. Stop pleading with him, bite your arm off if necessary rather than phone him. He says he wants space, give him space. Leave him to it for a few days. Let him make the first move to contact you.
Now when he talks to you act calm, pretend that everything is fine. Ask him how he is be civil, DON'T start blurting about how upset you are or can he come back home or blaming him or shouting. Scream inside instead if you must. The idea is to let him see what he is missing, that if he walks you are not going to fall apart, you will be just fine. That way he will see what he stands to lose by leaving.
If he comes round, book an appointment to go somewhere or take your child out later so that he can see you are getting on with life.
Don't let him think you want him because you can't live without him. Let him see you want him because of him. That you can get on quite fine but would prefer him in your life rather than out.
If he returns, then that's the time to get help with your issues. Spend more time together, maybe get counselling. Come up with a new strategy about money.
Good Luck. If he still decides to walk he's the loser. You will find happiness again without him. I guarantee it.