So I know that the Battle of Shasarazade is the point of no return. Mathiu is with a bunch of other people in the war room waiting for me to give the go-ahead to start the battle. I can no longer change out party members . . . is it over for me getting all 108? I have a save that's a few hours back which may help, but I want to know for sure.

I don't remember the exact point of no return for recruiting off-hand, but you might be. IIRC, there is an event that should happen there when you have all 108, so you might have just missed your chance.

Technically speaking the actual point of no return is when you speak to Mathiu after Shasarazade, but there are two specific characters (Leon and Mace) that need to be recruited prior to even going there or they disappear. The most you can have at this point is 106, the last two come after.