GI problems are an area where we're spoilt for choice for what could be amiss to cause them.
Gastroparesis doesn't generally prevent you from vomiting unless it is the result of fixing a hiatial hernia with a fundoplication procedure.
Where is the pain with this located? Same for the spasms too?
A standard upper endoscopy only looks as far as into the first portion of the duodenum so can miss any problem further in - a push enteroscopy or barium swallow test with small bowel follow through can check further down your system, but a Wireless Motility Capsule Test can be a more sensitive test to do (and could rule out any suggestion that it is "just IBS).
I assume you would have had a gastric emptying done to diagnose gastroparesis? Have you had an abdominal CT done too (preferably one with contrast and looking at the bowel arteries (mesenteric CTA or MRA to avoid the radiation)? Actually, a Doppler ultrasound of the mesenteric vessels is a good screening test to try first, and have any doctor listen to your epigastric sounds for any sign of a bruit. I'm suggesting these things as your symptoms can fit for being caused by either SMA Syndrome or Median Arcuate Ligament Syndrome, and not unusual to have a dodgy gallbladder function with these too, and often go for a number of years before eventually being diagnosed. If you happen to have EDS as well (or just hypermobile joints), that ticks another box for susceptibility to these.
As I say though, lots of other reasons for such symptoms and just with having had your gallbladder out, well that can be a minefield in itself from Post-cholecystectomy syndrome;
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3473449/