Hmm that's kinda tough. 100 multi to instruct is crazy - plus, the more desirable regionals will probably be interested in you by the time you've accumulated those hours. Any way you can just rent a multi and fly cross country with someone who is in a similar situation?
Is your 250 XC time adjusted for 135 (point to point)? That makes a big difference...I got an extra 80ish hours XC time.