Went and got the new (i.e. remanufactured) starter, and we discovered it was indeed the bendix. You could push it around easily with your finger and on the "new" one, it wouldn't budge. So it seems that was the problem all along! Husband admits he was worried because he'd had the old one bench-tested yesterday and it tested fine. So as soon as he gets some free time during daylight hours (no garage), he's gonna pop that one in and hopefully we'll be good to go