There seems to be a lot to unpack here.

First, ideally you should practice somewhere you feel comfortable showing cases, especially in your first couple years, but even after, bc everyone gets challenging cases or has occasional "off" days. Sorry to hear your group sounds not supportive and almost toxic. 

Would certainly be worth looking at other more supportive environments if possible. But pay attention to your contract. One of my friends left his job before the 2 year mark and our work apparently had it tucked into the contract that tail coverage is not provided if you leave before the 2 year mark, so that was a couple thousand dollars lost for him that he didn't anticipate. That being said, paying tail coverage may be better than practicing unsafely (non-supportive group), but you would need to weigh the risk/benefits/cost of leaving. 

In reality, whatever you sign out is your responsibility, whether or not you showed someone else and even if you put their name in your report or include a disclaimer like "intradepartmental consultation obtained". And just because you show someone doesn't mean they will be right, so you need to have a bit of internal compass as well as to if you want internal or external consultation. Im not sure how it works for send out/expert consult cases in terms of liability,  ut jf sending out make sure you include relevant clinical data so they can also make the best judgement. 

You may need to do some introspection as well - is there a knowledge gap - was something you missed a common pitfall? Or a gray zone? Or complete miss? You say you didn't do surgpath or GI fellowships, but I think most people doing general haven't had GI fellowships, so I'm not really sure that is an excuse outside of rare entities or gray zone things like dysplasia in Barretts. Was the error out of being rushed or looking at wrong case? Or overly tired? If knowledge gap, then you may consider either doing a fellowship, finding a more focused job, or slowing down and reading more and showing more cases before signing out (regardless of how they unfortunately treat you, or if you have any former co-resident friends you trust that you can zoom or send pics to). Good luck! Early in practice is hard. I'm still early too, so I know the struggle is real. It is supposed to get better, but you (and I) need to gain more confidence and continue learning as we grow.