Given your earning compared to your husband, I think that you will need to make a strong case to get maintenance for yourself too. You will need to draft your maintenance application with specific facts referring to the lifestyle that your husband is living, how he can afford it, why you cannot afford it, how you have got used to his lifestyle, why your son also needs to have the same standard of living as the father, etc. All this must be in detail and with evidentiary/documentary support. In that case, yes, you will most certainly qualify for maintenance and it can be substantial. As for your son, thats a given. How much? That too depends on the quality of your filings.
As for any limit under Sec. 125 Cr.P.C., I think that any limit of a few thousand rupees, if indeed there is such, then it is probably in theory but not in practice.