Sorry you had such a bad experience with the doc. Sometimes doctors seem to just make things worse. I wish medical schools did a better job of working on bedside manner! I've left many a doctor appointment in tears because the doctor was so insensitive. I would definitely find another GI doc before you go forward.
However, getting a colonoscopy to rule out Crohn's and other IBD is a good idea. The colonoscopy is really not that bad. I just recently had one, and I was really relieved afterward to find out that I didn't have any kind of IBD. My doctor had told me he thought I had Crohn's, and that was my worst nightmare too. The pre-colonoscopy cleansing process isn't fun, but you can do things to make it easier. You're knocked out for the test itself, so that's not so bad. I think that the chance of the instrument causing a tear is pretty slim--they just have to inform you of all of those possibilities in advance.
Also, from the little bit you mentioned about your symptoms, I'm wondering if you've been tested for celiac disease (a form of gluten intolerance). It may be helpful for you to have those tests as well (blood tests). But you need to make sure you go to a doctor that really understands celiac disease--many GI docs don't.
Best of luck figuring things out. I know it's a frustrating struggle.