Thanks everyone for the great responses!
First, to answer Sigaba's question - I discussed the side job with my Project Officer and he gave his approval, so that wasn't a problem.
As for the salary/stipend offered by our school, it is ridiculously low in my opinion. We are in a low-cost area of the country, but it is still much less than what I would expect most people to live on (roughly $1000/month stipend). My office mates are younger than I am, and most of them are living with multiple roommates and cutting costs down that way. My husband and I are living as frugally as possible, but we like having our own place and our own space. My office mates also still get some financial help from their parents. My parents don't really understand why I'm still in school at my age (early 30's). They come from a very blue collar town and I am definitely the only person from my high school to get a graduate degree, so they don't really see the purpose in it. That's not to say they aren't proud of me, but they don't see why they should still be helping me financially at my age. Not to mention, I really don't want to ask them for money. That puts extra pressure on me to not only pay my bills, but to have extra money to cover emergencies.
I am glad that TakeruK mentioned the international student conundrum. My husband is also an international student and unable to work at the moment, so it does become an expense. He is embarrassed by it - he wants to be the breadwinner. So I never mention to my office mates that I am really the one paying most of our expenses. I'm sure they assume that we have two incomes. He does do little odd jobs whenever he can find them to get a few hundred dollars here and there, and that helps. But he is not pulling a regular salary, and until he is I am the one who has to make sure we're covered. I am ok with the arrangement - we discussed it at length before we decided that we would both go for our graduate degrees in America.
You're right that I just shouldn't mention grants in front of them anymore, which is exactly what my husband said. When I brought it up I wasn't even thinking of it in terms of funding, I was just excited to be able to do the project that I proposed! I thought we could share in the excitement. But from now on, I will just keep my mouth shut and only discuss my dissertation with them. I realize I am lucky to be so well-funded, but I also worked very hard to get the funding I have and I don't appreciate anyone making me feel like I don't deserve it.
As far as the larger question of how much a grad student should be paid: it obviously varies quite a bit from school to school, but I think it is ridiculous to ask students to live below the poverty line. The result of such low stipends is that many students end up taking out loans to cover costs, which leads to graduating with massive debt. As Takeru said, we obviously shouldn't be paid as much as those who have graduated and are working in actual faculty positions, but the disparity is so great in some areas that there must be room for improvement.