Welcome here, I guess the reason you came is to have other people's perspectives, your own are driving you into serious illness. You give an account of one of those people full of determination, handling a full teaching load, supporting child and husband. You do this despite ill health plus what was in me an anxiety condition. Those feelings of self-doubt, guilt and an unrealistic fear of being fired sound very familiar.
You have been very strong, but you are not a never ending well of strenght, with no limits. You have approached and exceeded them, if that were not the case the guilt, pain, crying, anxiety, lack of hope and even posting here would not be happening.
To be blunt your husband sounds like another child, and a selfish one. Any sacrifice he could have made for your mum's funeral would have been worth it, and soaking up your money overseas whilst continuing to be unfaithful is simply not on. When you became ill he did not remain as a financial and emotional support but disappeared. You are a source of money, not a wife.
I'm sorry to say it that way, however I don't know of any other way of putting it. Do you think I'm judging to harshly? Love, duty and custom can tend to blind.
Your health with proper treatment, your well being and your child are the most important things, and true you do need money for that. Plus you do need a sense of accomplishment, which you get in the classroom. I could make the obvious suggestions, however I think you can too. How can you decrease your load and still have enough for those essentials I just listed?
Again being blunt, if your health fails completely, either due to mental or physical illness what happens?
You are remarkable and I've tried to give a realistic reply, and am sorry if I upset you, you do not deserve that. I hope it allows you pause to think between what at first glance may seem unacceptable alternatives, I would welcome your response.