You don't really understand concurrent users - but don't feel bad, nobody does
It (effectively) means Apache (or whatever you are using) processes in memory *at the same time*. This means the maximum number of people who click on something in Moodle within a few seconds of each other (very approximately). So, 150 people accessing a SCORM resource over 2-3 hours which, as Marcus points out, is nearly entirely client side will have a concurrency nowhere near 150 (my guess would be 10-20).
So, yes, you have an even bigger problem than you think. I would suggest that the number of users, in itself, isn't the issue. I have no idea what though - you are going to have to do lots more testing on the server to get some clues.