Maximum PBX stack exceeded

That sounds extremely cumbersome no matter how you do it. Do you actually have DID's in all those area codes and is that why you have all the outbound routes? Otherwise, there are probably ways to consolidate your outbound routes down if you simply want to send 7 digit caller id - especially if you have the same 7 digit DID in different area codes. If you absolutely can't, you might have to look at using the commercial 'class of service' module instead of extension routes which might be more robust at handling what you are trying to do.