First, I'm so sorry that your DH was robbed and I'm glad he's OK. You guys are having legitimate life problems and need to deal with them. Your life, your problems, your security - that's what you have to devote those resources to.
And you're not heartless. Your SIL is a never-ending black hole of neediness, no matter how much cash, energy, love, time, etc., you throw at her, it will never be enough. She will always come back with escalating needs, not so much because she actually requires those things to be happy/healthy, but because that's what proves your love to her. You putting your foot down and saying no is the only thing that will help remove you from the cycle.
You did the right thing. Many many many hugs.