You asked two questions. First, jobs you could hope to get. You know that the market for recent PhDs in academia is bleak, but that doesn't mean there are no jobs. If you get accepted to a reasonable graduate program and find yourself a good advisor (this is more important), then there should be some hope of jobs in academia at the end of the tunnel. They might be jobs with high teaching loads, or jobs in locations you don't want to live, but they do exist. Have you thought about how much you're willing to pick up everything and move? Have you thought about whether or not you'd be okay teaching introductory calculus over and over again to students who don't care all that much?
Let's talk about jobs outside academia. The biggest employer of mathematicians in the world is the National Security Agency. They employ research mathematicians and would view any knowledge of computer science as a massive bonus. I believe that if you made it clear to them that you wanted to do mathematics research then they wouldn't force you to do software engineering. You still wouldn't get to pick your own problems, but by now you are used to that. I'm sure the NSA has a wide variety of problems you could work on, and that you could find something sufficiently mathematical, but where a good understanding of theoretical computer science, computer hardware, etc would be an asset. Cryptography is a nice way to combine algebra and computer science, and if you could get a job in Crypt then you could probably do as much algebra as you want. There are also surprising ways to use Differential Geometry in real-world applications, after representing a data set of interest as a bunch of vectors in some giant space. There are also a ton of NSA contractors, the biggest of which is the IDA (Institute for Defense Analyses). If you do some googling, you can find a large pool of employers here, and many will employ you even if you just have a masters degree in mathematics.
Another place which no one has discussed in depth yet is Microsoft Research. The Boston office in particular is very good and has employed many amazing pure mathematicians (e.g. Laszlo Lovasz, Vera Sos, etc). They tend to be graph theorists, but they have complete freedom to work on whatever they want. There are other employees whose sole job it is to figure out ways to apply what the mathematicians are doing. The person running this branch is a very good mathematician named Jennifer Chayes, and I learned everything I wrote in this paragraph from a talk I saw her give. The problem here is that they seem to only hire rock-stars for full-time positions. It's a bit easier to get a summer internship there (even for non-graph-theorists; I know an algebraic geometer who got one), and you might be able to parlay that into a job. But you'd need to be in grad school at the time.
Hedge funds are starting to hire mathematicians again. This is also a profession which would like someone with a background in software engineering. I believe one thing mathematicians do at Hedge funds is find ways to do simple computer operations faster. Unfortunately, this would probably be a place where you wouldn't be using the algebra or differential geometry you studied in grad school. Have you ever considered a career in finance?
Next, how to get into graduate school. I'm a graduate student at Wesleyan University, which has a tradition of taking on non-traditional students. When I got here we had a 65 year old man as a PhD student. You want to find a place like that. I think Wesleyan is moving in a different direction now, but I believe Montana State University is another which might work. To be such a student, you need to have great letters of recommendation, but they probably don't have to be from famous research mathematicians. I agree with Suvrit that you should take courses at a University near you, and try to get both advice about which programs to apply to and a good letter of recommendation out of that. If your other letters are from people you've worked for, and they talk about your work-ethic, your attention to detail, your mental toughness, your drive, etc then I think you'll be fine.
Many undergraduates have sought my advice about graduate school over the years. I always try to get at their real motivations. Being bored with your current job is not enough to get you through grad school. The only really acceptable reason to go is if you love learning mathematics, problem solving, and doing research (or if you have a strong reason to think you will love it when you get to it). Going to grad school just so you have a credential to open up new job avenues is a sure-fire way to either drop out or end up in a job where you are a slave to your teaching. It might be worth considering getting a masters somewhere first and then deciding if you really want the PhD. It's a big time commitment and during that time you're making almost no money. At your age, I feel like this would be a strong disincentive. With a masters degree a lot of doors are opened up (e.g. NSA) which might not be open right now because you've been out of math for so long. Here are 2 good articles about grad school, which should help you sort out your real motivations and see if it's the right thing: first, second. Two good books for trying to get you through it are: Krantz, Peters (not all the advice in here is good, some is for non-mathematicians only).
To end on a positive note, if your soul-searching tells you that grad school is right for you and you can't truly be happy doing anything other than mathematical research, then clearly you have to go. If that comes about, let me just say that I think that your years outside of academia will give you a very valuable perspective and motivation. I've noticed that grad students who worked for a few years after undergrad usually came back for good reasons and with great work-habits. They were able to use those to get through the down times while those who came directly from undergrad struggled because they were never sure if the grass on the other side was greener. I'd encourage you to really own those years you spent outside academia and not see them as a mistake when you're working alongside much younger people. Plus, if you do apply for jobs at small liberal arts schools after graduating, they might like you more for the perspective you bring and your increased ability to advise undergrads.