AC has met its obligation by offering a reroute or a refund. If OP has a specific proposal for a reroute on another carrier, he should certainly make that proposal to AC, but AC is not obligated to do so.

As to what I presume is an extra car service at IST because OP and his friend now arrive at different times, that's simply not going to get covered.

After the trip, OP could file a whine with AC and perhaps get some form of CS gesture.