When are feeding tubes used?

Hi, I am newly diagnosed with gp. It started kind of suddenly in June of this year. I got diagnosed by gastric emptying study and my specialist said that based on that and my symptoms I have very severe gastroparesis. I have lost 50 lbs over these last 6 months. The thing is I was slightly overweight when I developed gastroparesis so now I am in the healthy bmi range. My GI doctor and PCP say that since I am a healthy BMI it doesn’t matter that I lost that much weight or how fast. I keep steadily losing weight. I am at the point where I can’t eat any amount of food solid or even my nutrition drinks without bad pain for about 6 hours. At this point Im drinking 400-800 calories a day, in constant pain, sleep for 12 hours a day and can’t do anything or go anywhere. I have to use a cane to stand up and to walk. At what point is a feeding tube used? I’m assuming it is only used once you are very very skinny? I read something written by a GI GP specialize saying it should be used even in overweight people when a certain percentage of their bodyweight is lost over a certain timeframe. Is it true that it is only when you are very skinny regardless of symptoms lack of nutrition weight loss etc?