Well, it's a shock and totally unexpected, but he can still have a happy life and he will be the same dog you love.
It sounds like he needs to wear a male doggy diaper (malewrap, also called belly band) for his incontinence. That will keep him dry and protect your surfaces. Malewraps are your friend and much less fuss than a diaper.
You may also want to ask the vet about expressing his bladder. That is where you squeeze his tummy to make him urinate. If you empty him that way several times a day, it will keep him dryer.
Dogs with rear paralysis do well pulling themselves around at home, but for exercise you can get him a little wheelchair. It will be easy with him being a small breed dog.
You might enjoy reading some of the posts by sunspirit
. Her pug Tucker has hemivertebrae and she has been taking care of him since 2006. They got ramps first when he began having problems, and then a wheelchair. Here is a link to the ramps, and I'll attach a photo of Tucker. He must be around 11 years old now. You can see by the sweet look on his face he has been enjoying life all these years.viewtopic.php?f=4&t=8821&p=45180&hilit=ramps#p45180