Wellness Weight Management is only 19% protein dry matter. It isn't the worst food for liver problems... It does have chicken in it which may not be great but at least it doesn't have red meat. If you don't want to go with a pres. diet, don't.
It is your choice. The L/D canned isn't the worst food in the world though. For kibble, the Royal Canin Hepatic LS 14 is better than the L/D. My Yorkie got terribly itchy from this food though.
Wysong makes a canned SENIOR food that is lower protein.
For snacks you can give apple bits (peeled), watermelon, white potato (peeled and cooked), sweet potato (peeled and cooked), zuccini, carrot, green beans. I prefer to cook the carrot but you could also pulverize it.