I have had Gastroparesis for about 14 years. My Gastric Emptying results grade my Gastroparesis as severe. The severity of my symptoms however vary, and I’ve had times where it’s been very bad and other times where I’ve felt relatively well for long periods of time. What’s interesting to note is that the severity of your symptoms and the severity of your gastric retention rate do not always correlate. This has been the case for me.
As far as treatment, I started on Reglan, but later (after several years) developed a reaction to it (Tardive dyskinesia), and am no longer on it. I was placed with a gastric stimulator in 2002, which greatly helps to control my nausea and vomiting. It has also reduced the number of times I end up in the ER for GP episodes. I later had my gastric stimulator replaced in 2012 due to the battery running out. It last approximately 10 years, depending on how high you have the setting. I also take Zofran and some other medications which help out.
Diet and insulin changes are also important. What you can eat/tolerate varies for each person, but generally a low fiber, low fat, low carb diet. Seeing a nutritionist/diabetes educator helped me a lot with this. Also, they will likely have you take your insulin doses differently to better match up to your digestion. For example, some meals I split my insulin dose 50/50 over an hour. It will be different for each person though.