My pup was an indifferent eater, but I found out it was because I was feeding him
crap (Purina one)
. I never force fed him; since his weight was stable and he had no issues with hypoglycemia, I just left the food out and if he ate, great, if he didn't, he was getting enough snacks (that he did like) to maintain. He would vomit a couple of times a week, but I (in my ignorance) chalked it up to him being a toy breed. Anyway, I changed him to a much higher quality food after joining YT and realizing the error of my ways (he was almost 4 years old at that time) and once I put him on Blue Buffalo Freedom, he became much more enthusiastic about eating and has quit vomiting.
I agree with the others that force feeding seems quite extreme and I would stop that and change his food. You will be amazed at the difference!