The reason the opto will not key the IC-730 is because the PTT relay pulls almost 80 ma compared to 5 - 10 ma of most newer radios. The opto can't handle that much current. The fix is to put a darlington configured transistor after the opto to help it along. Any NPN transistor capable of 100ma or more will work. 2n4123, 2n2222, mps-a06, etc. I've done 6 or 7 interfaces for ic-730's and they all worked fine after putting the darlington arrangement after the opto.
If someone can tell me how to post a pdf to this forum I could throw up a drawing.