So for ~$10 you have two wide angle lenses for the Camera you don't have yet. =). Yes the marking on the Vivitar means Olympus mount. I had an OM1 when they first came out and didn't care for the SS around the lens mount. Didn't like Nikkormats either, same configuration.
Depending on the size of your hands any OM may be too small to hold comfortably, then the winder comes in handy, even if you don't want one.
These critters are much smaller than the Canon you had.
The crack in the 1.8 will likely have no visible effect. You're going to need to shoot it to find out.
BTW OM1n would be my choice if I went that way.