Guardian visa

No you would not be able to work in Malaysia while on a Guardian visa.

You will need to show a good level of offshore income with proof from the employer, bank etc. to get the visa. I am not sure how high this currently is, but it could be RM7-10k per month equivalent. The COL in Malaysia would probably see your monthly minimum spend at about RM5k including education.

Once you have enrolled your son in an international school, they will provide documents and tell you the procedure. They might introduce you to a company who can help you make the application. It will require both parents to be involved in making the application - i.e. parental permission from the child's father.

It is not possible to attend a government school in Malaysia as a foreigner, so there will be quite a lot of fees involved in obtaining an education. These involve enrolment fees as well as tuition and equipment fees. There is the Global International Indian School in Brickfields, if you want to make some equiries.