kcfonman has a good suggestion with IVR. What you have to work with now won't really solve your problem.
I'll try to help clear up some of your other questions:
Since you don't have package 327, you can't do RAN broadcast. That would have let you have multiple callers on a RAN trunk listening to a recording. You are limited to a one-to-one connection between caller and trunk without it. You can have multiple trunks in a RAN route, which would help a little. MIRAN cards really work best with RAN broadcast, since then you can use those features they advertise.
ACDNs and CDNs both count toward the same limit. A CDN is a "Control DN" programmed in LD 23. It is used by applications like Symposium and Call Pilot, which actually "control" those CDNs and direct calls to themselves, monitor activity, etc.
When you look at your SLT printout, you will see a limit of 24000 ACDNs. That actually derives from 240 ACDNs per customer, and a maximum 100 customers per system (240 x 100 = 24000). Release 25 introduced ACD DN/CDN Expansion (package 388) that can expand that from 240 to 1000 with the requisite hardware in place. An excerpt from the Release 25 Feature Summary document: The Automatic Call Distribution Directory Number/Control Directory Number Expansion feature (ACDE Package 388)increases the allowable number of ACD DNs and/or CDNs on a Meridian 1 Option 81C CP PII system from 240 to a maximum of 1000 for each customer.The number of customer groups remains at 100 and the system level total of configurable ACD DN/CDNs remains the same at 24,000.
Your license for ACD sets is 500, and 1000 for TNs. The 1200 that you see is the maximum number of ACD set licenses that you can purchase for an Option 61C (assuming you had the TNs and the hardware to support that many!). You also have a license for 500 ASTs. Those are not ACD sets, although they are most frequently used in a contact center environment (such as providing screenpops to ACD agents, etc.) It enables a third-party application to monitor TNs (similar to what Symposium or Call Pilot does with CDNs). It looks like whoever engineered your PBX anticipated that you might implement some third-party application some day, since ASTs licenses are not free by any means.
Hope this helps answer some of your questions..