Today's update: I realized that I couldn't get the starter out without removing the idler arm, and the idler arm wouldn't come out without the cross member removed, so we dropped the cross member.
I was mistaken, before: my new starter has 3 bolt holes. I just thought that one of them was a post, but it was actually a bolt coming through from the 'back' side that I didn't see initially.
Only bolt left blocking me on the starter is the upper bolt. I can get my crow's foot onto it, but the clearance is so tight, I can't actually get any of my adapters onto the crow's foot. I need to buy a compact flex-joint for it, and maybe a 3/8ths socket wrench as well, and see if that will let me reach it.
(oh, if anyone is really curious: I'm posting what I'm doing to Instagram under 'guildhallgarage' because I'm really damn bored lately. It's pretty terrible photos, but hey, you're probably bored too.)