How to get specific guidance from busy advisor? I need to graduate this semester, my master's project is far behind schedule, and I'm not getting the guidance I want from my advisor. How can I work with him to handle this productively?

I have to defend my thesis in two months because my funding will be gone after this semester. I have zero data because my project is computer-based and involves an initial stage of bringing a simulation into equilibrium, after which we can get usable results. I've been working on this preliminary phase since June and it's still far from our "usable" threshold. In the meantime, I've been working on everything I can do without final data (practicing trial analyses, writing a literature review and methods section).

I'm getting only vague guidance from my advisor, who is admittedly very busy. He has a large research group, administrative responsibilities and outside collaborations, so I certainly understand that my project can't be his first priority. He told me that I have to graduate this semester. I've kept him updated about the project status and my current steps, and he says that is all "fine" and I'm doing the right things, but that it's impossible to predict when the simulation might work, and "that's just how research is." I've expressed my concerns more than once, and he's typically responded by telling me not to "over-think things" and not to "freak out." At our most recent meeting, I said that I doubt the simulation will be working in the next few weeks and asked what I should do in that case--he said "you still have two months, we'll just have to see what happens." 

My advisor is well-established and respected in his field. He has a strong track record of graduating students, and he's certainly more experienced and knows much more about research than I do. I should trust him when he says everything is fine, but it doesn't seem fine to me. I can't realistically expect everything to start working in the next few weeks when I've made insufficient progress for eight months so far. I have no backup plan for what to do without the data.

How can I express my concerns so that my advisor will listen? How can I do better at getting specific guidance?

Edit to update:
I did reach out to other students and postdocs for help on the technical issues, and I've been doing that since June as well. 

Edit for how it all turned out:
I talked again with some other students, and came up with a new strategy. My advisor was a little skeptical but agreed we could try it. Luckily the new approach turned out much better. He is still too busy to give the project much attention, but as long as I can finish the entire project and write up everything in a month (no stress, right??) I should be fine!
Your advisor will not solve your problem - at least it is very unlikely! Digging very deep in the specifics of such a simulation is something a person in such a position just don't have the time to - and sometimes even not the detailed knowledge, e.g. regarding frameworks used, implementation details etc.! 

One question you should adress is: Will (s)he accept negative results? If you can describe all steps you did, explain why things did not work as planned, do you still have a chance for a good grade? If "yes", then really everything is fine, you "just" have to work hard and document all your attempts.

If "no", you should try to get help from a graduate student or post-doc working in a similar field. But still keep your advisor updated about everything you do.