If you have stollen enough, while you might not have a reputation in particular holds, you can still have a hit put on you that will be carried out by thugs, or someone hiring bandits to get what you have.
As you point out, it seems you are not alone.
Marriage Ceremony: During your marriage ceremony, after your spouse gives his/her vows, they will sometimes randomly leave the temple while Maramal is still talking, and will disappear, not to be found anywhere. This can be solved if you quickly leave the ceremony and initiate the conversation with your spouse about where you should live.
There are fairly detailed guide here that provides a few details that may help you. As with any such bugs, it may end up that console commands are your only way out. A few things I'd suggest:
Be sure to own a house before re-attempting the marriage. It's possible you are not given the "Where do you want to live" dialog if you don't own a house. Since initiating that dialog has fixed the glitch for some folks, owning a home could be key.
After the Marriage, the partner will ask where the player wants to live, giving him/her the choice between the partner's house or in The Dragonborn's house, if applicable.
Get cold feet and skip the whole ceremony. That may reset somethings and work it out for your next attempt. Wait 24 hours (in game) and try again.
If the player misses his Wedding Ceremony, they can approach the intended partner and ask for another chance. Maramal will then agree to host another ceremony, the next day.
There are more fish in the sea. Try another lucky lad or lass. The bug may be specific to the NPC you've chosen.
Use the console. You may have to do some experimenting. Remember to save before any console witchcraft, as it can create as many bugs as it fixes. The wiki provides several options, but the most appropriate seems to breakup using:
completequest 0007431B
resetquest 0007431B
resetquest 00021382
setrelationshiprank player 4
Then re-propose, and hopefully on the next run through it will work out. I'm summarizing significantly, and I haven't tested this myself, so I strongly suggest you read the Wiki.
Best Answer
Maramal can be found in Riften. He is either in the Temple of Mara or the Bee and Barb. Sometimes I see him roaming the market as well.
Here's a quote from the UESP wiki regarding Maramal:
And yes, Ysolda can be married.