Good Morning and welcome to Just answer. I am Dr. Loretta, a licensed veterinarian and I am happy to answer your question.
Fatty tumors are common in older dogs especially if they are a bit over weight. There is no ay to avoid these except to keep your guy on the thinner side but, even if you do this, your dog's body, if prone to these, may still get them. These are harmless and will only be removed if the interfere with function. There is no way to prevent these from occurring. As far as the eating grass, this is a normal way for dogs to keep them selves regular...they will eat grass to force the vomiting to regulate their system. This also is not harmful to your guy unless he does this several times every day. Intermittent episodes is normal. Does that help?
Regulate their system? what does that mean?
If they feel nauseous, the grass will stimulate the vomiting that , in turn , makes him feel better. All dogs do this at certain times because of stress or something he ingested that did not agree with him....once he vomits, he feels better from a minor digestive disturbance. Does that make sense?