Well, the prior marriage wouldn't appear - at this point - to have worried Immigration too much since you did get your PR card.

To explain where I'm going with this:

Under the terms of the I-864 Affidavit of Support, you can actually sue your husband for support. It doesn't matter that your marriage is very short, or if you do get divorced - the obligation remains until one of these things happens:

1. You die;
2. You leave the country permanently (abandon your residency)
3. You naturalize (become a US citizen)
4. You earn 40 "qualifying" SS quarters (basically work for 10 years)

Immigrants have successfully sued in Federal court for this support up to the tune of 125% of the Federal Poverty Level - for two people (you and your son), currently about $1500/month. Though some courts have required the sponsored immigrant to mitigate (look for work, etc.,), other decisions determined that the immigrant was not required to do so.

So...given that you're the primary caregiver, and you would get at least child support (outside of what you may or may not be able to get if you do decide to sue via the I-864) I'm seeing distinct possibilities in which you can remain in the US AND your child can have regular access to both parents - and that's surely best for the child, yes?