If you don't want the Married title and you have no way to convince Grisham, you can just run from him instead of talking to him or waiting for the ceremony to begin, but then all of Modoc will turn hostile.
You cannot disband your spouse.
You get your new spouse for a companion even if you're already at your companion limit, but if you then kick someone out you can't get them back again unless you kick another one out in their stead.
After you are married you will no longer be able to guard the brahmin or sell Bess if you didn't do that already.
You can let your spouse work for the Golden Globes for 3 dollars.
If you want to sell your companions in at the Slaver's Guild in the Den, you have to sell your spouse before you can sell other companions.