My 15 1/2 Yr Old Setter Mix Has Been Getting

My 15 1/2 yr old setter mix has been getting ahold of toilet paper. He drinks a lot of water and urinates with ease when taken outside. He vomits hs food if I give him his normal amount of dry and canned mixed so I now give him canned in small amounts. He is not deficating his normal amount. A couple of days ago there was some paper in his stool. I read online to give him pureed pumpkin or stool softeners. Is this age or is there something else try. My smaller dog had surgery a month ago for eating parts of a plastic chew bone. It was tough on her and very costly. At 15 1/5, I really don't want to opt for surgery if there is another option.